A man in his 20s apparently drowned in a residential pool in Upper Marlboro early Sunday, and Prince George’s County police said they do not suspect foul play.

Cpl. Evan Baxter, a police spokesman, called the case a death investigation, meaning there is no obvious natural cause.

Around 1:30 a.m., police and rescue workers responded to a report of a drowning in the 4200 block of Crain Highway SE, but when they arrived there was no one in the pool. Two hours later, they responded to another call at the same home. This time, fire department spokesman Mark Brady said, they found the victim already receiving CPR.