BRIDGEWATER, Mass. (AP)—Two killers serving life sentences escaped from prison Sunday and anxious police told residents to cancel Halloween trick or treating.

Robert Dellelo, 51, and Joseph Correia, 38, were discovered missing from the Massachusetts Correctional Institution during a noon head count, police Officer Robert Fernandes said.

Robin Bavaro, a spokeswoman for the Corrections Department, would not comment on how they escaped or when they were last seen.

Authorities said they were considered extremely dangerous and urged residents not to let their children outside.

‘‘I haven’t had a trick-or-treater yet, and usually I’ve had a million of them by this time,’‘ Selectman John J. Colford said shortly after dark.

‘‘People are concerned, but I don’t think frightened,’‘ he said.

A daytime parade by costumed children went off as scheduled, though attendance was down. Organizers blamed cold and rainy weather.

But residents were jittery.

‘‘I have the doors locked, believe me,’‘ said Joanne Potwin, a taxi dispatcher.

Colford said residents are accustomed to living near the prison complex, which includes a mental hospital where suspects are evaluated to determine if they are competent enough to stand trial.

Escapes aren’t new, either.

Albert DeSalvo, the alleged Boston Strangler, broke out of Bridgewater State Hospital in 1967 along with two other inmates, touching off the biggest manhunt in Massachusetts history. He was recaptured within days and was later found dead in prison.

Dellelo was convicted of killing a Boston police officer during a 1963 jewelry store holdup. He has been in prison since 1964. Correia, who was convicted in a 1976 bank robbery in Boston in which a security guard was killed, has been in prison since 1976.

One resident who reported seeing the two identified them from mug shots, Fernandes said. Another resident reported seeing two men wearing jeans in the woods around 2:30 p.m., police said.

‘‘They looked like they were scared, like they were anxious or something, like they were out of place,’‘ said Rebecca Treloar, who said she saw the two before hearing of the escape.

‘‘When I found out they had escaped, it scared me half to death,’‘ Treloar said.

More than 70 police and correctional officers using dogs scoured the wooded area, Fernandes said. Motorists were stopped and their trunks searched, and police knocked on doors in search of the two.

A whistle blew every half hour to tell residents the convicts still were at large.