US authorities have arrested a suspect near Boston after reports of blasts and the fatal shooting of a police officer on the campus of MIT. It is unclear if the incidents are linked to Monday's Boston bombing.
Police arrested at least one man early Friday in the Massachusetts town of Watertown, just eight miles (12 kilometers) west of downtown Boston. Local television showed images of a suspect lying face down on the ground, surrounded by the authorities.
There were reports of gunfire and explosions in the same neighborhood by eyewitnesses and reporters on site, according to local television.
Authorities have told residents to stay indoors and "remain away from windows," according to a statement. They were reportedly searching for a second suspect.
The Boston metropolitan area has remained on high alert since early this week, when two deadly explosions at the city's annual marathon left three dead and over 170 other people injured.
While the motive behind the terror attack remains unknown, FBI officials were finally able to release photos of two suspects late Thursday in what they hoped would lead to a turning point in the case.
MIT shooting leaves one dead
Shortly before the Watertown standoff, local and state police had responded to the fatal shooting of a campus security officer at the Massachusetts Institute of Technology (MIT) in nearby Cambridge, Massachusetts.
MIT is located in Cambridge, Massachusetts, across the Charles River from Boston.
University officials lifted the lockdown several hours later, but advised students to "remain vigilant in the coming hours," according to a statement posted on the university's official website.
"MIT Police have determined that the suspect in this evening's shooting is no longer on campus," the statement said.
A spokesperson from the district attorney's office said authorities doubted the shooting had a connection to two deadly explosions that left three dead and over 170 wounded at the Boston Marathon earlier this week.
However, none of the investigators could dismiss the possibility "with 100 percent certainty at this time," Middlesex County District Attorney's office spokesperson David Procopio told the news agency Reuters.
kms/ipj (AP, AFP, Reuters, dpa)