Eds: Restores background, adds that Boston mayor says suspect is in boat. Will be updated.
WATERTOWN, Mass. (AP) — Gunfire erupted Friday night amid the manhunt for the surviving suspect in the Boston Marathon bombing, and police in armored vehicles and tactical gear rushed into the Watertown neighborhood in a possible break in the case.
The burst of activity came at the end of a tense day in and around Boston, and less than an hour after police announced that they were scaling back the hunt because they had come up empty-handed following an all-day search that sent thousands of SWAT team officers into the streets and paralyzed the metropolitan area.
Less than an hour after the hail of gunfire, a round of blasts could be heard. A state police spokesman said only that the activity was related to the search for 19-year-old college student Dzhokhar Tsarnaev.
Boston Mayor Tom Menino told WBZ-TV the suspect was holed up in a boat parked in a backyard. Reporters were being kept away from the scene and a message left for Menino's spokeswoman wasn't immediately returned.
Before the gunfire, State Police Col. Timothy Alben said at a news conference that he believed Tsarnaev was still in Massachusetts because of his ties to the area. But authorities lifted the stay-indoors warning for people in the Boston area, and the transit system started running again by evening.
"We can't continue to lockdown an entire city or an entire state," Alben said. At the same time, he and other authorities warned that Tsarnaev is a killer and that people should be vigilant.
Tsarnaev fled on foot after a furious overnight gun battle that left 200 spent rounds behind and after a wild car chase in which he and his brother hurled explosives at police, authorities said. His brother, 26-year-old Tamerlan Tsarnaev, died in the shootout, run over by his younger brother in a car as he lay wounded, according to investigators.