Image copyright Getty Images Image caption The girl told a bus driver of her worries on her way home (file picture)

A Pennsylvania couple was found dead in their home after their seven-year-old girl went to school and told a bus driver she could not wake them.

Christopher Dilley, 26, and Jessica Lally, 25, died of suspected drug overdoses, police said.

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

The girl went to school and told a bus driver on the way home that something was wrong with her parents.

Investigators found Mr Dilley and Ms Lally's bodies on Monday evening.

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.

Ms Lally's sister told told NBC affiliate WPXI she tried to intervene over concerns of the children's safety earlier this year.

"My sister wasn't the person she became when it came to drugs," Courtney Lally said. "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's sister said she planned to attend a hearing on Wednesday to try to win temporary custody of the children.

The McKeesport School District issued a statement following the incident: "Our school district took immediate action after we were notified of the concerns shared by one of our students on their route home."

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

Authorities told WPXI they had responded to a suspected heroin overdose on the same street hours earlier, underscoring the epidemic of drug overdoses in both Allegheny County and nationwide.

Last year, there were 422 opioid-overdose deaths in Allegheny County, which includes McKeesport and Pittsburgh, a recent county health department report. found.

Across the country, more than 28,000 people died from overdoses of opioids such as heroin and prescription pain relievers in 2014, which was more than any year on record, according to the Centers of Disease Control and Prevention

The national problem with drug overdose made headlines last month when Ohio police released a graphic photo of a couple overdosing on heroin while the woman's four-year-old son sat in the backseat.