Weston, 51, served eight years in prison for killing a 25-year-old man who starved to death in her North Philadelphia apartment in 1981. She was sentenced in 1985.
Also arrested Sunday were Weston's boyfriend, Thomas Gregory, 47, of North Philadelphia, and Eddie Wright, 49, who police said is homeless. They are charged with criminal conspiracy, aggravated assault, kidnapping, unlawful restraint, and related offenses.
Investigators said they expect more charges will be filed as they piece together a timeline of the operation, which took place over at least a year and in several states. Police also face the daunting task of locating the owners of the identification documents in Weston's possession.
It is not known how Weston got in contact with the victims, how she managed to start collecting their checks, or how long she had been holding them captive, Evers said.
"I think it'll be some time before this all comes out," he said.
In addition to the neglect and malnutrition the victims endured, police also were investigating any possible physical abuse.
The victims - three men and a woman ranging in age from 29 to 40 - are being treated for undernourishment at area facilities and are under close watch.
"You can't get any lower than how they preyed on these people," Evers said of Weston and her alleged accomplices.
Police were in the process of finding relatives and said Monday that two of the victims were from Philadelphia. The woman, identified by CBS3 as Tamara Breeden, was reported missing in 2005 by her family. CBS3 also identified one man as Derwin McLemire.
One of the men is believed to be from North Carolina and was also missing for some time, Evers said.
"The relatives are just falling down on the floor to hear that these people were found," Evers said.
Police also asked for the public's help in finding relatives of victim Herbert Knowles, 40. People in Norfolk, Va., saw his photograph in the media Monday and contacted police.
The group is believed to have come to Philadelphia within the last month from Palm Beach, Fla., where Weston has a home. Police believe they moved suddenly to avoid authorities there. Before that, authorities think, the group may have been in Texas.
Florida authorities have begun sending Philadelphia police fliers with names of missing persons, Evers said, and the FBI has been called in to assist with out-of-state aspects of the investigation.
"We have to trace the steps of this the entire way," said FBI Special Agent J.J. Klaver. "We have to determine exactly what happened. You've got a horrific crime here. You've got vulnerable people who were severely mistreated."
Arthur C. Evans, commissioner of Philadelphia's Department of Behavioral Health and Intellectual Disability Services, said city officials would not discuss the case until they had learned more about it.
"We don't know what happened in this particular case," Evans said.
He and Kathy Sykes, Philadelphia's director for intellectual disability services, said the city does intake work for people with such disabilities who apply for a state and federally funded waiver program that helps pay for residential and other services, including rehabilitation support and in-home help. About 3,000 people participate in the waiver program, and it has a waiting list of several thousand. Applicants must have an IQ of 70 or less, Evans said. An average IQ is 100.
Most people with intellectual disabilities also are eligible for Social Security disability payments.
The investigation began Saturday with the discovery of the adults trapped in a fetid subbasement police likened to a "dungeon" in a building at 4724 Longshore Ave., where Weston's son and daughter live. They have been cooperating with police and have not been charged.
Turgut Gozleveli, the building's landlord, told police tenants had started complaining of suspicious people coming and going in the building.
When Gozleveli searched the basement, he found a door leading to a 10-by-15-foot space with a dirt floor. Inside were makeshift beds with blankets, as well as two small dogs. When Gozleveli shone a flashlight over the blankets, he said Sunday, "People's faces just started coming up."
The men and woman were thin and had bedsores. The room was empty except for the beds, a container of orange juice, and bathroom buckets. At least one of the men was chained to a water heater, police said.
Contact staff writer Allison Steele at 215-854-2641 or firstname.lastname@example.org.
Inquirer staff writer Miriam Hill contributed to this article.