Police secure an area near the Massachusetts Institute of Technology campus in Cambridge, Mass. (AP)
Update, 2:40 a.m.
CAMBRIDGE, Mass. (CBS) - Police have converged on a neighborhood outside Boston where there were reports of explosives being detonated, and police were telling reporters to turn off their cell phones.
Dozens of officers and National Guard members are in Watertown, where media outlets report that gunfire and explosions have been heard. A helicopter is circling overhead.
Authorities early Friday were calling for somebody to get on the ground and put their hands up and a loud thud was heard after someone shouted "fire in the hole."
Reporters are being told to move away from the scene. A police officer told a reporter: "If you want to live, turn off your cell phone."
An employee of CBS Boston station WBZ-TV on the scene says one person has been taken into custody. Another suspect was reported to be at large.
Late Thursday night, a campus police officer was shot and killed at MIT, and authorities were searching for the person or people responsible. There was no word whether the developments in Watertown were connected to the shooting.
At 2 a.m., MIT posted an alert on their website saying that the suspect in the shooting was no longer on campus, WBZ says.
CAMBRIDGE, Mass. (AP) - Police at the Massachusetts Institute of Technology say a suspect in the fatal shooting of an officer is no longer on campus.
No arrests have been made in the MIT officer's shooting. The shooter is being sought.
But MIT said Friday on its website it's now "safe to resume normal activities."
Still, it's urging its 11,000 students to "remain vigilant." It had earlier warned them to stay indoors when the shooter was on campus.
The MIT officer was shot Thursday night on the prestigious university's campus just outside Boston. He was pronounced dead later at a hospital.
The shooting comes just days after twin bombings at the Boston Marathon finish line killed three people, wounded more than 180 others and led to an increase in security in the region.