Police are investigating a woman charged with locking four mentally challenged adults in a filthy Philadelphia cellar in order to collect their social security checks.

Philadelphia police said Monday that Linda Ann Weston, 51, had identification records of as many as 50 people when she was arrested Sunday, suggesting she might have defrauded dozens of people in several states.

She, her boyfriend Gregory Thomas, 47, and Eddie Wright, 49, who police say is homeless, were arrested Sunday and charged with keeping three men and a woman -- aged 29 to 40 -- locked in a squalid basement.

Police found the captives on Saturday in a basement space with a dirt floor and some makeshift beds. They were undernourished and had bed sores, and at least one of the men was chained to a water heater, police said.

"You can't get any lower than how they preyed on these people," Philadelphia Police Lieutenant Ray Evers said.

Local news station CBS 3 reported that the four captives had the mental capacity of 10-year-olds and had been missing for some time, with one reported missing in 2005.

"The relatives are just falling down on the floor to hear that these people were found," Evers said.

Weston had previously served eight years in prison for killing a 25-year-old man who starved to death in her Philadelphia apartment in 1981. She was sentenced in 1985.

She and her alleged accomplices are believed to have come to Philadelphia within the last month from Palm Beach, Florida, where Weston has a home.

Police believe they may have fled law enforcement, and that they may have operated fraud schemes in other states. The Federal Bureau of Investigation (FBI) is also taking part in the investigation.

"We have to trace the steps of this the entire way," said FBI Special Agent JJ Klaver. "We have to determine exactly what happened. You've got a horrific crime here. You've got vulnerable people who were severely mistreated."