A pilot and his wife have died of an apparent drug overdose, authorities said.

The bodies of Brian J Halye, 36, and 34-year-old Courtney A Halye were found by their children Thursday morning in Centerville, Ohio, about 50 miles north of Cincinnati.

One of the four children living in the home, ages 13, 11, 10 and 9, found the couple unconscious on the floor of their upstairs bedroom and called police.

An unidentified 13-year-old boy told the dispatcher: 'My two parents, I just woke up, and my parents are on the floor. My sister said they are not waking up.'

He said his parents had been fine the night before.

The bodies of Brian J Halye, 36, (left) and Courtney A Halye, 34, (right) were found Thursday

Courtney Halye (left) had a history of drug abuse and had threatened suicide, relatives said

The couple was found in their home (pictured) on East Von Dette Circle in Centerville, Ohio

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One of the three girls also called police and told to the dispatcher: 'My mom's on the floor and my stepdad ... they're not waking up ... we just woke up for school.'

Brian and Courtney Halye each had two children from previous relationships, Centerville police said.

Courtney Halye's former husband and father of her two children, Jacob Castor, died in August 2007 at age 27 from an accidental overdose, according to the Montgomery County Coroner’s Office.

Brian Halye was a pilot for Spirit Airlines, which told the Dayton Daily News that Halye last flew March 10.

The preliminary cause of the couple's death appears to be an accidental overdose of fentanyl, an opiate many times more powerful than heroin, said Montgomery County Coroner's Office Director Ken Betz.

On Thursday, the United Nations labelled fentanyl, the drug responsible for the death of musician Prince last year, as one of the most dangerous substances in the world.

Two ingredients used to the make the drug fentanyl were added to the United Nations's international list of controlled substances.

A final determination on the cause and manner of the couple's death will take six weeks until toxicology reports are completed, Betz added.

Drug paraphernalia was found inside the home, Centerville police said.

Nancy Casey, Courtney Halye's mother, contacted police in January 2016 because she felt her daughter was abusing drugs and had threatened to harm herself.

Halye had been "hooked on drugs" on and off for about seven years, Casey told police.

Halye's mother told NBC News that her daughter was a Type 1 diabetic, being treated for depression and had been prescribed medication.

Brian Halye also contacted police in January 2016, this time to report his wife missing.

He found Courtney Halye locked in their home, the Dayton Daily News reports. He worried she might use the two unloaded guns he kept inside so he forced entry.

Brian and Courtney Halye (pictured) each had two children from previous relationships

When Brian Halye got inside the house his wife was holding both guns, according to the police report.

He took them from her before police arrived.

Police said she appeared either intoxicated or having a medical issue related to diabetes. She was taken to the hospital for treatment.

Brian Halye told officers that his wife had battled heroin and cocaine addiction 'for quite some time'.

Courtney Halye was convicted of a drug possession charge that was later expunged in 2010, the Dayton Daily News reports.

Courtney Halye's mother, Nancy Casey, said her daughter (left) was a Type 1 diabetic, being treated for depression and had been prescribed medication. She added that Brian (right) had last flown on March 10

Since January, Montgomery County has had 165 accidental drug overdoses, with heroin, fentanyl and carfentanil being the current fatal mix of drugs most seen by Betz.

In nearby Columbus and surrounding Franklin County, Fentanyl has already figured in 55 overdoses in January and February - one fatal overdose a day, NBC News reports.

Brian Halye's two daughters were picked up by their mother from the scene Thursday morning, police said.

Warren County Court records show he was divorced in 2011 in a joint custody case.

The Halyes purchased their home on East Von Dette Circle in Centerville during the summer of 2013.

The neighborhood, Pellbrook Farm, is a quiet suburban cul-de-sac, with homes valued around $150,000 to $225,000.