As hundreds of heavily armed police continued their massive manhunt for Dzhokar Tsarnaev, the second suspect in Monday's bombing of the Boston Marathon, the Boston area was ordered shut down with all public transportation suspended.

A train that left New York's Pennsylvania station for the South Station in Boston was stopped in Providence, about a 50-minutes drive from the Boston area, at about 11:20am.

Massachusetts Governor Deval Patrick ordered businesses closed in Watertown, Newtown, Waltham, Belmont, Cambridge and Boston on Friday morning, and law-enforcement officials told people to stay indoors.

Public schools and colleges in the area - including Boston College, Harvard University and Massachusetts Institute of Technology - were closed.

"I feel safe to stay at home now, especially Friday morning (after 10:30am) as less police cars and sirens are around," said a 24-year-old Harvard graduate student who asked to be identified only by her last name, Zhang.

She lives about a 10-minute walk from where MIT campus police officer Sean Collier, 26, was shot and killed during a confrontation with the two bombing suspects Thursday night.

"Collier was a hero who spotted the two suspects, but I was so sad to hear he lost his life, so sad," said Zhang, who attended a memorial last night for Lu Lingzhi, the 23-year-old Boston University graduate student who was one of the three people killed in the marathon blast that also injured more than 170 people.

Police told residents to stay indoors as they went door-to-door in Watertown for the 19-year-old immigrant from Kyrgyzstan, whose older brother Tamerlan was shot and killed in Thursday's night's police chase.

"He could be anywhere, it's true," said Hugh Clement, the Providence police chief.

By the time the FBI released the photo of the at-large suspect, his picture wa already all over the city of Providenc, including the Providence railroad station.

"We've got several calls from people who think they've seen someone who looks like him," Clement told China Daily.