"We do not comment on ongoing investigations, but obviously the death of anyone in a DPW-licensed facility or DPW-supervised situation is of concern, thus the reason for investigating such deaths," said Race.
The probe could take several weeks, he said. In addition, Montgomery County prosecutors are also considering possible criminal charges.
A landlord found Jerry Snavely, 62, and John Malkasian, 53, in a Norristown apartment on July 9. The landlord and a neighbor said all the windows in the apartment were closed and that a box fan wasn't turned on.
John Snyder, 56, was found in his bedroom in a Pennsburg rooming house on July 12. His windows were also shut. All had schizophrenia.
Meanwhile, the investigation continues at the Woods Services in Middletown where a 20-year-old autistic man, Bryan Nevins, died of hyperthermia after being left in a van on July 24. Prosecutors are exploring possible criminal charges.
On Thursday, Woods Services reinstated one of two suspended counselors who had taken Nevins and three other clients on a day trip to Sesame Place last Saturday
Woods cleared the male counselor after an internal investigation, said spokeswoman Cheryl Kauffman. The female counselor remains suspended.
State law requires that employees at residential treatment centers have a high school diploma or general education development certificate. Staff members are subject to criminal background checks and must complete 30 hours of training within 120 days after they are hired and before they begin working with children.
Employees with regular and significant direct contact with children must complete an additional 40 hours of training each year in areas of fires safety, first aid, crisis intervention, suicide prevention and other areas specified by the employer.
Pennsylvania also requires that all children 21 or under be checked at least every hour whether sleeping or awake.
Kauffman would not provide information about the training of the two counselors involved in Nevins' death, saying it was part of the ongoing investigation.
Contact staff writer Julia Terruso at 610-313-8110 or jterruso@phillynews.com.Inquirer staff writer Derrick Nunnally contributed to this article.