Update - Nov. 25, 6:55 p.m. ET:
"New Haven is safe. The Yale campus is safe," New Haven Police Chief Dean Esserman said.
No gunman was found after a room-by-room search on campus, he said, and no one was injured in the suspected hoax.
"Though it is starting to tilt in the direction of an innocent mistake, it started with a purposeful and malicious call," Esserman told reporters.
Update - Nov. 25., 4:00 p.m. ET:
The lockdown on the Yale campus has been lifted with the exception of Old Campus and Calhoun College, and officials suspect that 911 call was unsubstantiated.
New Haven police received a phone call at 9:48 a.m. Monday from an anonymous man who said his roommate was heading toward the Yale campus with a gun, and intended to shoot people, Courant reports.
The call was made from a phone booth on Columbus Avenue, between Howard Avenue and Hallock Street.
The caller did not identify himself and only stayed on the phone with dispatchers for a few seconds, NBC Connecticut reports.
Police have not yet identified the caller. At a press conference, Esserman said, "The new haven police are going to find ... and we're going to put handcuffs on the person who made that call."
New Haven Police spokesperson David Harman said that two witnesses on Yale campus told officers that they saw a person holding a "long gun," but it's possible the witnesses saw a police official holding the gun instead.
The search was still underway at 3:30 p.m., and the possible gunman had not been identified. Roads surrounding the campus remain closed.
This afternoon, police searched all residential colleges.
Police will be searching all residential colleges, says Martha Highsmith, senior adviser to President Salovey.
Yale Daily News
@yaledailynews
Police will be searching all residential colleges, says Martha Highsmith, senior adviser to President Salovey.
SWAT team officers, border patrol, the Department of Homeland Secuirty, and the New Haven police were all brought in to find the possible gunman.
Border patrol and Department of Homeland Security on the scene, says NBC.
Yale Daily News
@yaledailynews
Border patrol and Department of Homeland Security on the scene, says NBC.
The Yale PD conducted room-to-room searches.
YPD: "When they knock on your door, a Yale Police Officer will slip their Yale ID under the door. Please cooperate."
Yale Daily News
@yaledailynews
YPD: "When they knock on your door, a Yale Police Officer will slip their Yale ID under the door. Please cooperate."
Police are going to search for Yale gunman room by room
Eric Rodriguez
@erod393
Police are going to search for Yale gunman room by room
Guns drawn by officers in Calhoun college... Yale is absolutely crazy today, wish I could've gone home for break!
500 Yen
@TheTownsFinest
Guns drawn by officers in Calhoun college... Yale is absolutely crazy today, wish I could've gone home for break!
Special Weapons and Tactics officers walk the Yale Campus after lockdown in response to reports of a gunman.
Maggie Jordan
@MaggieJordanACN
Special Weapons and Tactics officers walk the Yale Campus after lockdown in response to reports of a gunman.
Earlier this morning, Yale University posted the following message on its website and sent a campus-wide text message confirming "reports of a person with a gun on/near Old Campus."
Here are the text alerts my friend received from @Yale about gunman on campus #yale #thv11
Elle Mohs
@ElleMohs
Here are the text alerts my friend received from @Yale about gunman on campus #yale #thv11
A loudspeaker announcement advised students to take shelter.
Just heard loud speaker announcement on Elm St. advising students to take shelter. #yale @NBCConnecticut
Audrey Washington
@AudreyNBC
Just heard loud speaker announcement on Elm St. advising students to take shelter. #yale @NBCConnecticut
Yale alert system sends out call reporting man on campus with a gun. reports unconfirmed, but ypd and nhpd investigating
Marek Ramilo
@marekramilo
Yale alert system sends out call reporting man on campus with a gun. reports unconfirmed, but ypd and nhpd investigating
Tons of police cars on the streets here at Yale... Police telling us to get out of the windows
Yah Yah
@TheTownsFinest
Tons of police cars on the streets here at Yale... Police telling us to get out of the windows
Yale confirmed sighting of the gunman on or near "Old Campus" at 11:06 a.m.
Confirmed report of a person w/ gun on/near Old Campus. SHELTER IN PLACE. http://t.co/GWOeIeUZgu
Yale University
@Yale
Confirmed report of a person w/ gun on/near Old Campus. SHELTER IN PLACE. http://t.co/GWOeIeUZgu
SWAT team officers were reported on campus around 11:15 a.m.
SWAT teams sighted on Old Campus.
Yale Daily News
@yaledailynews
SWAT teams sighted on Old Campus.
There's a gunman roaming the campus here @ Yale... There are teams of police officers with M16s outside of my window
Yah Yah
@TheTownsFinest
There's a gunman roaming the campus here @ Yale... There are teams of police officers with M16s outside of my window
FBI on High near Crown @yale #yale. Report of gunman.
CourantPhotographers
@CourantPhotogs
FBI on High near Crown @yale #yale. Report of gunman.
@NBCConnecticut SWAT team on Old Campus at Yale
Kendall Polan
@kendallpolan
@NBCConnecticut SWAT team on Old Campus at Yale
Exclusive:Yale security questioned this man. Don't know if he is connected to Yale emergency@NBCConnecticut
Audrey Washington
@AudreyNBC
Exclusive:Yale security questioned this man. Don't know if he is connected to Yale emergency@NBCConnecticut
Roads around the school are closed.
Elm street shutdown. @NBCConnecticut #yale
Audrey Washington
@AudreyNBC
Elm street shutdown. @NBCConnecticut #yale
Map of road closures via @NBCConnecticut. Please stay away from the area and shelter in place #yale #nhv
hiddenCT
@hiddenCT
Map of road closures via @NBCConnecticut. Please stay away from the area and shelter in place #yale #nhv
Road closures in New Haven via @NBCConnecticut @Yale #nhv #yale
hiddenCT
@hiddenCT
Road closures in New Haven via @NBCConnecticut @Yale #nhv #yale
Maria Bouffard, director of emergency management, confirmed that the New Haven Police Department and university police officers are at the scene.
Bouffard said that updates will continue to be posted on the university's official emergency services website as they are received.
We're in the middle of a gunman chase here at Yale...
Easton Kawawaki
@Eassttt
We're in the middle of a gunman chase here at Yale...
@Yale
Ayana Harry FoxCT
@AyanaHarry
@Yale
One officer told an NBC reporter that the gunman was "somewhere in this vicinity," and told her to "get out."
Officer on scene told me: "he's somewhere in this vicinity. Get out!"@NBCConnecticut
Audrey Washington
@AudreyNBC
Officer on scene told me:
"he's somewhere in this vicinity. Get out!"@NBCConnecticut
Police officers confirmed that as of 11:39 a.m., no shots were fired.
NHPD Lieutenant Jeff Hoffman confirms no shootings, no injuries.
Yale Daily News
@yaledailynews
NHPD Lieutenant Jeff Hoffman confirms no shootings, no injuries.
The lockdown was on effect most of the day, but lifted around 3:10 p.m.
Just got a text and phone call from Yale Alert. 11:55 am, lockdown still in FULL EFFECT on Old Campus.
Jasmine
@WHOAitsJasmine
Just got a text and phone call from Yale Alert. 11:55 am, lockdown still in FULL EFFECT on Old Campus.
Lockdown lifted outside of Old Campus and Calhoun College.
Yale Daily News
@yaledailynews
Lockdown lifted outside of Old Campus and Calhoun College.
Police are letting students walk to Union Station.
Yale Daily News
@yaledailynews
Police are letting students walk to Union Station.
Dean Esserman at press briefing: "Nobody has been hurt, nobody has been found. But the day is hardly over."
Yale Daily News
@yaledailynews
Dean Esserman at press briefing: "Nobody has been hurt, nobody has been found. But the day is hardly over."