Police detained the female resident of the Greenwood Health Center on Wednesday morning, police Lt. Michael Manzi said. But Police Chief Bruce Marquis said the woman has not been questioned in the fire, in which 10 people died and 23 were hurt.
"We are unable to interview that individual right now because that person is under the care of medical professionals and thus deemed not stable at this moment," Marquis said.
Police also were seeking a search warrant. Investigators "have not determined a cause or origin" for the fire, he said. "We're going to interview a lot of folks."
The 148 patients at the home included the elderly, mentally handicapped and a young man who had been in a coma for three years. Mayor Eddie Perez said the facility also handled younger psychiatric patients.
The mayor said a nursing supervisor, three nurses and eight nurses' aides were on duty when the fire erupted early Wednesday.
Nurses, police officers, firefighters and ambulance workers saved more than 130 people, hauling patients on stretchers, wheelchairs or beds into the frigid outside air.
The fire damaged two sections of the single-story, brick building. As of late Wednesday, at least 10 people injured in the fire were in critical condition.
Firefighters said this was the worst fire they had seen, because it struck in the middle of the night while the frail and disabled residents were sleeping, and because of the single-digit temperatures outside.
"You know that no one is going to be a position to rescue themselves," Fire Capt. Terry Waller said.
Marcia McCrorey said her mother, 64-year-old Phyllis Kendall, has been a resident of the home for 11 years. Her mother was partially paralyzed because of spinal meningitis.
McCrorey said her mother called her after the fire, using the cellular telephone of a family friend.
"She said, `I smelled smoke and I started screaming for somebody to come get me, come get me,"' McCrorey said. She said her mother heard fire doors closing and began to weep.
Family members flooded the facility's parking lot in the hours after the fire, peering into the home's windows in hopes of spotting loved ones. After several hours, Debbie and Donald Duford finally found her 53-year-old brother, Bill Carroll, a mentally retarded man with a lung ailment.
"We expected the worst, but reminded ourselves that he was ambulatory," she said. "He said he wasn't scared."
Luis Henriquez held a silver-framed school photo of his 17-year-old son, who had been in a coma for three years.
"One of the ministers told me he didn't make it," he said.
Daniel Henriquez was among the eight victim names released by the city Wednesday evening.
Fire Marshal William Abbott said there was no sprinkler system in the building, but said it was up to code and fire extinguishers were present. He said it was not clear whether the building had a "grandfathered" exemption from sprinkler requirements or was exempt from them because of its layout or occupancy.