Easter morning brought flames, cold and a search for housing to residents of a 36-unit building on Route 110, where a two-alarm fire early yesterday morning sent 10 people to the hospital and left dozens at least temporarily homeless.

Firefighters were called to the Walkway Condominiums, at 333 First Street Blvd., next to the Duck Island water-treatment plant in the Centralville section of the city, about 4:30 a.m., and had to rescue several people from second- and third-floor porches.

Fire Chief Edward Pitta said about 10 people were taken to local hospitals for treatment of smoke inhalation, though none of the injuries was believed to be serious.

By last night, Kat Powers, a spokeswoman for the American Red Cross of Eastern Massachusetts, said 55 residents of the complex registered for assistance at a shelter established by the Red Cross and the city at the Lowell Senior Center on Fletcher Street.

Pitta and City Manager Bernie Lynch said it remained unclear last night how long it will be before residents can return to the building. At a minimum, electricity and the building's fire alarms will have to be restored.

Officials were expected to tour the damage today to determine what else may need to be done.

"Hopefully, we can get them back in sooner rather than later," Lynch said.

Pitta said the fire's point of origin had been isolated to an area near a heater in a first-floor apartment, but added that the cause remains under investigation by the Fire Investigation Unit.

"From what we know at this point, it doesn't appear suspicious," Pitta said.

He said the fire started in a first-floor apartment, then extended to the second- and third-floor apartments above it. Those three units were completely burned-out, and there was smoke damage throughout much of the rest of the building.

Pitta said the fire was under control in about an hour.

Many residents were awakened by smoke alarms. At least one resident, however, said no alarms went off in her section of the building. Rather, she was awakened by the commotion outside.