New York City police are investigating the death of a man found unconscious, with a head injury, under a mattress at a hotel blocks from the Empire State Building.

Officers were called to the Hilton Garden Inn on West 35th Street at around 4 a.m. Monday. Police say the unresponsive man had suffered trauma to the back of his head.

He was taken to a hospital, where he was pronounced dead.

Investigators and medical examiners are working to determine how he died. Police believe he was in his 30s.

A hotel manager hasn't immediately returned a call.

The 298-room hotel is near Herald Square and Penn Station in a part of midtown Manhattan bustling with both tourists and business travelers.