PEORIA, Ariz. — A young couple babysitting the man’s 5-month-old nephew told investigators they forgot they’d left him in their car for about four hours after dropping off his mother at work, police said Monday.

The boy was pronounced dead at a hospital where he was taken after the couple retrieved him from the car left Sunday in an unshaded parking spot, police said in a probable cause statement.

Jose Garcia Jr., 18, and Monique Avila, 23, told police they forgot about the boy, who was in a car seat behind the driver’s seat, after they returned from taking the boy’s mother, Garcia’s sister, to work late Sunday morning, the statement said.

When they went back to the car in the afternoon to pick up the mother, they discovered the unresponsive boy and took into the apartment, where they tried unsuccessfully to revive him by placing him in front of an air vent and by pouring cold water on him, police said in the statement.

Garcia and Avila were jailed on suspicion of child abuse. It wasn’t clear whether they had attorneys who could comment on the allegations.

The probable-cause statement said police determined that outside temperatures rose from the mid 70s to the mid 80s between Sunday morning and afternoon when the boy was in the car and that the temperature inside the car about four hours after the boy died was over 100 degrees.

“Even with lower temperatures (Sunday), it’s still possible for vehicles to get extremely hot,” said Officer Brandon Sheffert, a police department spokesman.

The Maricopa County Medical Examiner’s Office will determine the cause of death.