LAKEWOOD, Wash. -- A 2-month-old baby girl who spent the night sleeping in a car with her parents in Lakewood has died.

Lakewood police Lt. Heidi Hoffman said the parents reported their daughter was unresponsive when they woke up Wednesday after 6 a.m. in a relative's driveway on Lake Louise Drive.

The parents drove to St. Claire hospital in Lakewood where the baby was pronounced dead.

Detectives questioned the 29-year-old father and 27-year-old mother, but no one was arrested.

The parents told investigators that the relative wasn't home, so they decided to sleep parked in the driveway. The baby girl was sleeping in a child seat, and the engine was left running to keep the vehicle warm overnight.

Officials said there were no obvious signs of trauma, and they are not calling the death suspicious.

An autopsy performed Wednesday afternoon failed to determine how the girl died, and toxicology tests will be performed to see if carbon monoxide poisoning may have been a factor in the baby's death.

The test results may not be back for several weeks.