THE INVESTIGATION into the Kensington fire that killed two firefighters Monday could take more than a week, Fire Commissioner Lloyd Ayers said Wednesday.

"There are tons and tons of rubble in there, beams partially burned," Ayers said of the former five-story Thomas W. Buck Hosiery warehouse, at Jasper and York streets. "All of those things have to be carefully examined. . . . It's a very arduous process."

He said that it was important to first get a crane at the site to remove hazardous material there. A task force consisting of the Fire Marshal's Office, police and the Bureau of Alcohol, Tobacco, Firearms and Explosives was able to start looking around only on Tuesday, Ayers said.

"We have to be really solid with the investigation," he said. "I've tried to ask for a cause - 'Hey how we making out out there?' - and you learn you can't rush."

The fire, which erupted in the old, vacant warehouse, was reported at 3:13 a.m. and reached five alarms in less than an hour. Lt. Robert Neary, 59, and firefighter Daniel Sweeney, 25, were inside an adjacent furniture store when a roof and wall of the furniture store collapsed, killing them in an avalanche of debris.

Two other firefighters who also were in the furniture store, Francis Cheney, 43, and Pat Nally, 26, were taken to Temple University Hospital for treatment. Cheney was released Monday. Nally remained in fair condition Wednesday.

On Wednesday, Cheney's mother told the Daily News about the phone call she received about 6:30 a.m. Monday from her son.

"It didn't sound like him," Pat Cheney said, speaking in the Bustleton home she shares with her husband and son.

"He said, 'There's been a terrible fire and it's still going on,' and he said, 'I don't know where the rest of them are. I think they're dead,' " she recalled.

With tears forming in her eyes, Pat Cheney said that her "heart goes out to the other families. I just can't even imagine what they're going through."

Hers is a family of firefighters. Her husband, Frank Cheney, retired as a captain in the Fire Department in October 2003, after having served 40 years.

Pat Cheney said that her son, who is also a nurse and paramedic, had gone to New York City when the 9/11 attacks occurred to help with the rescue efforts. At the time, he was sitting in a nursing-school class, and when he learned of the tragedy, "he left, didn't say anything to anybody and took the next train" to New York, she said.