A Pennsylvania couple have been found dead in their home after their seven-year-old daughter went to school and on her way home told the bus driver that she could not wake them.

Christopher Dilley, 26, and Jessica Lally, 25, died of suspected drug overdoses, police said after their bodies were found on Monday evening.

Three other children - aged nine months, three and five - were also found inside the home in McKeesport.

The three children were unharmed, but taken to hospital and later placed into the custody of the Allegheny County's Office of Children, Youth and Families.

Lally's sister, Courtney Lally, said she had tried to get help for the couple's children months ago, but Jessica became furious and moved the family to McKeesport.

Speaking to local news channel, WPXI, Ms Lally said: "I feel like if I wouldn't have done that, it would have been way different and we could have made up months ago, and she'd be here today."

Ms Lally continued: "My sister wasn't the person she became when it came to drugs. She wasn't the person I knew.

"It was like the drugs had taken over and at first we didn't know it was heroin.

"She loved her kids - she did. She loved her mom, she loved me, she loved us."

Ms Lally added that along with her mother she plans to attend a hearing to try and win temporary custody of the children.

Neighbours said that they did not witness anything unusual at the property.

"Our school district took immediate action after we were notified of the concerns shared by one of our students on their route home," the McKeesport School District said in a statement.

"We alerted all appropriate officials and ensured the students' safety.

"Each school in our district offers counseling to any student who needs it.

"We will be available for the family affected by this tragedy."