SAN JOSE -- Authorities are investigating what caused a man's death after his body was found at a city park Saturday morning.

Officers responded to a 6 a.m. call after a passer-by walking through Northwood Park located an unresponsive man on the ground, said San Jose Police Officer Jose Garcia.

Paramedics responded to the scene off Guildhall Drive but were unable to revive the man who appeared to be in his 30s. The victim was pronounced dead at the scene.

The man's identity is being withheld pending his identification by the Santa Clara County Medical Examiner-Coroner's office.

The man's cause of death remained under investigation late Saturday morning, but Garcia said a preliminary investigation revealed no foul play was involved.

No additional details were released.

Anyone with information about this case is urged to call the San Jose Police Department's 24-hour non-emergency line at (408) 277-8900.

Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.