This is a breaking news story. Check back for updates.
UPDATE 5:03 p.m. EST: The lockdown at Yale University has been lifted in its entirety. "The Shelter-in-place/lock-down has been lifted," the school said.
UPDATE 3:47 p.m. EST: Yale has lifted the lockdown for Calhoun College, but the shelter-in-place order remains in effect for Old Campus.
UPDATE 2:01 p.m. EST: Authorities are checking rooms on the Yale campus. The school gave the following advice to students who may still be on campus (Yale is on Thanksgiving break and many students headed home.):
"Out of an abundance of caution, Police will be doing a room to room search starting with the residential college areas. When they knock on your door, a Yale Police Officer will slip their Yale ID under the door. Please cooperate. In some cases, Police may use keys, but they will identify themselves. Shelter in Place continues."
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UPDATE 1:40 p.m. EST: Although there is still an active investigation on the Yale campus, New Haven police said no shots have been fired, NBC Connecticut reported. There are also no suspects in custody.
According to New Haven television station WTNH, a person called 911 and told a dispatcher that their roommate threatened to shoot people on the Yale campus.
"There was nothing specific about the threat," New Haven police spokesman David Hartman told the station. Hartman said two witnesses also reported seeing a person with a gun, described either as a rifle or shotgun.
UPDATE 12:10 p.m. EST: In the latest update from the emergency section of Yale's website, the university said the lockdown remains in place.
"There are confirmed reports of a person with a gun on campus on the Old Campus. The shelter-in-place/lockdown continues," the message read. "Teams from Yale Police, New Haven and the State Police are on the scene and are actively searching for any gunman. THIS IS NOT A TEST. Call 911 with any information."
While the school said the alleged gunman was seen in the vicinity of Old Campus, authorities have set up a perimeter that includes "pretty much all of the Yale campus," a New Haven dispatcher told the Boston Globe.
UPDATE 11:48 a.m. EST: Yale sent out the following updated emergency message on its website:
"SHELTER IN PLACE/LOCKDOWN REMAINS ON CAMPUS. IF OFF CAMPUS, STAY AWAY."
A person with a gun has been reported Monday on the Old Campus at Yale University, prompting the school to alert anyone on the New Haven, Conn., campus to shelter in place.
At 11:02 a.m. EST, Yale sent the following text message to students:
“Confirmed report of person with a gun on/near Old Campus. SHELTER IN PLACE. This is NOT a test.”
An earlier message sent to what the school called the “Yale community” said the report was unconfirmed:
“New Haven Police have received an anonymous call from a phone booth in the 300 block of Columbus Avenue (between Howard Avenue and Hallock Street) reporting a person on the Yale Campus with a gun,” the message read. “There have been NO confirmations or sightings of this person. Yale and New Haven Police are in the area. If you have information, please call 911 immediately. The Yale Police Department advises those on campus to remain in their current location until there is additional information.”