Grass Valley police said they're investigating a man's death at a park as a homicide. 

Around 7 a.m. Saturday, police were called to the temporary skateboard park in Condon Park for a report of a person on the ground.

When they arrived, officers found a deceased man believed to be in his 30s, police said.

Grass Valley police said they called the FBI Evidence Response Team for help collecting "key articles of interest." Investigators from the Nevada County District Attorney's Office were also at the scene.

"Multiple pieces of evidence were discovered, and this case is now being investigated as a homicide," the police department said late Saturday night. 

No arrests have been made.

Police said the identity of the person is being determined, and his identity will be released once the next of kin is notified. 

The area was closed as investigators collected evidence on Saturday.