A teenage girl died last week after an incident at a group home in Delaware run by a for-profit company, AdvoServ, whose long record of problematic treatment ProPublica chronicled last year.

Attorney Chris Gowen, who has a lawsuit against AdvoServ concerning a different teen, said he has learned workers were manually restraining the girl when she became unresponsive. He and his clients have spoken to current and former workers about the incident.

“While we await further information we do hope that a full investigation into this latest incident occurs,” he said.

AdvoServ did not answer questions about the death. A spokesman declined to say whether the girl was being held down – manually restrained – before staff called 911.

“Our staff is heartbroken over the loss of a young woman in our care, and our deepest sympathies go out to her mother and extended family,” the company said in a brief statement.

The spokesman said mechanical restraint devices, which include wrist and ankle cuffs, were not involved in the Delaware death and are not used in group homes in that state anymore.

The girl, whose name state police did not release, died Wednesday in a Delaware hospital, two days after an ambulance took her from the home for youth with developmental or intellectual disabilities and serious behavior challenges.

Delaware state police and regulators also haven’t said what happened to the 15-year-old from Maryland. The state medical examiner’s office is conducting an autopsy, but a spokeswoman said the results will not be made public.

Maryland is one of several states that send difficult cases to AdvoServ because they cannot find beds and schooling closer to home. The company, which is owned by a private equity firm, is based in Delaware and reported last year that it cared for roughly 700 children and adults in that state, Florida, and New Jersey, and was expanding into Virginia.

Gowen filed a lawsuit this summer in Delaware against AdvoServ , on behalf of a young resident who says he was left unsupervised and raped repeatedly by other clients at AdvoServ homes during more than four years there. His neck was also injured during a restraint performed by workers.

“[W]e learned of a significant number of instances where improper restraints were used involving our client,” Gowen said.

Delaware state police and the state agency charged with licensing group homes and investigating abuse in institutions are looking into the girl’s death. Asked whether Delaware regulators were taking steps to sanction the company or putting extra precautions in place to ensure children’s safety there, Delaware Department of Services for Children, Youth and their Families spokeswoman Dawn Thompson said the agency had begun an inquiry: “Once completed we will determine any next steps if warranted.”

The girl is not the first child to die under questionable circumstances at AdvoServ’s homes and schools.

In 2013, Paige Lunsford, 14 and autistic, died at the company’s Florida complex after a night in which she was restrained – at times latched to a bed and chair – while she vomited repeatedly. And in 1997, 14-year-old Jon Henley, who was autistic and had epilepsy, was found dead in his bed one morning after an apparent seizure. An autopsy revealed low levels of anti-seizure medication in his blood.

Regulators in multiple states have fielded decades of complaints of abuse, neglect and inadequate medical care at AdvoServ facilities.

Leslie Seid Margolis, a managing attorney with Disability Rights Maryland, said she has raised concerns about AdvoServ’s care in Delaware dating back a decade. Her agency, which represents people with disabilities, has received multiple complaints about AdvoServ – including two that came in last fall alleging sexual and physical abuse.

Margolis said that a few years before, she had obtained a copy of AdvoServ’s policies for its Delaware homes – which she described as “draconian.” They outlined the use of measures including wrist, waist and ankle restraints.

“Every kind of restraint you could imagine,” she said. “It was horrifying.”

Maryland eventually told AdvoServ it could no longer use mechanical restraints on children from the state.

A former worker for AdvoServ in Delaware, who asked that his name not be used, said he left three years ago in part because he felt staff did not receive enough training in deescalating conflicts or restraining clients.

The company had been trying out new restraint procedures that were supposed to make restraints less forceful by involving more staff members. But, he said, with too few staff often available to carry out the restraints as planned, “It just becomes unsafe.”

In response to the worker’s comments, AdvoServ’s spokesman pointed out that he left three years ago, but did not elaborate further.

The company is one of the few group home operators that still use restraint devices to confine clients who become aggressive. As ProPublica has reported, AdvoServ staff used such mechanical restraints on clients at its 200-bed campus northwest of Orlando roughly 28,000 times.

Florida officials said in June that they were moving clients out of AdvoServ’s complex and stationing an investigator there to provide extra oversight during the transition, which they expected to take months.