Officer Christine O'Brien, a department spokeswoman, says a daughter of alleged ringleader Linda Weston was arrested early Wednesday.
O'Brien says detectives had been interviewing the daughter about the case and she was put under arrest around 3:45 a.m.
Police are not releasing her name, but say she will face similar charges as the other three arrested.
Linda Weston, 51, was charged Monday with kidnapping, false imprisonment and other offenses after her landlord stumbled on the four adults, all weak and malnourished, in a dank, foul-smelling boiler room over the weekend. Her bail was set at $2.5 million.
Also charged were Gregory Thomas, 47, whom Weston described as her boyfriend, and Eddie "the Rev. Ed" Wright, 50.
This comes as a special task force, trying to sort out a widening investigation into that basement dungeon in Philadelphia, is talking to at least 10 more people.
Philadelphia police - acting on a tip from Florida authorities - searched for and took into protective custody six juveniles and four young adults believed to be related to the suspects and possibly the victims on Tuesday evening.
The 10 were found at various locations throughout the Frankford section of the city.
They range in age from 2 to 19 years old.
"We've found 6 juveniles and 4 young adults that were somehow blood related or related to the victims or the defendants in this investigation," Lt. Ray Evers of the Philadelphia Police Department said.
The 10 are being interviewed and being checked out medically. They group includes 19-year-old Beatrice Weston, the niece of alleged ringleader Linda Weston. Beatrice has been missing since 2009 and was said to have been physically abused.
"She is in very, very poor condition. She has lost a lot of weight. She has newer injuries, definitely some older injuries, a lot of scarring," Evers said.
A task force is working around the clock to try and locate as many as 50 victims of the alleged fraud and kidnapping ring that is said to have spanned a number of states including Texas, Florida, North Carolina, Virginia, and now Pennsylvania.
Authorities have also determined that one of the captives being held in the subbasement in Tacony, 29-year-old Tamara Breeden, bore two children who are believed to have been among those recovered today in Frankford.
Those children are expected to be reunited with their mother in the next day or so.
There are multiple agencies working on this task force with Philadelphia police including the FBI and authorities in West Palm Beach.
The case began Saturday morning when landlord Turgut Gozleveli discovered the victims after he heard dogs barking. The door to the basement room was chained shut, but Gozleveli got inside and lifted a pile of blankets to find several sets of eyes staring back at him. One man was chained to the boiler.
Police identified the victims as Derwin McLemire, 41, of North Carolina; Herbert Knowles, 40 of Virginia; and Tamara Breeden, 29, and Edwin Sanabria, 31, both of Philadelphia.
Detectives also found dozens of identification cards, power-of-attorney forms and other documents. Philadelphia police formed a task force to investigate the case as authorities try to find as many as 50 more possible fraud victims, Officer Jillian Russell said.
Knowles was reported missing in Norfolk in December 2008. According to an investigatory report by Norfolk police, Knowles' mental health case worker reported him missing when she couldn't reach him and family members failed to hear from him.
The Associated Press contributed to this report.