LOS ANGELES (Reuters) - Detectives have uncovered evidence that a Hollywood studio executive who mysteriously vanished 10 months ago was murdered, even though they have yet to find his body, law enforcement officials said on Thursday.

Gavin Smith, a 57-year-old film distribution executive for 20th Century Fox, was last seen on the night of May 1, 2012, driving in his black Mercedes Benz away from a friend's house in Oak Park, northwest of Los Angeles.

Authorities issued a missing person bulletin for Smith, also known for playing on UCLA's 1975 national championship basketball team under legendary coach John Wooden, and asked for the public's help in finding him.

But the discovery of Smith's car in a storage facility in February led to a break in the case, Los Angeles County Sheriff's spokesman Steve Whitmore said.

"This is a significant change in this case," Whitmore said. "The fact that they found the car, the condition of the car. Preliminarily, they believe Gavin Smith was murdered. The evidence is pretty sound."

Whitmore said detectives had also established what they believe was the motive for Smith's slaying, but he declined to discuss it further.

"They pretty much know what's going on," he said.

Police following a tip recovered the car in Simi Valley, about 20 miles by freeway from the unidentified friend's home in Oak Park. Smith's body has not been recovered.

The facility where the car was found was linked to a man currently being held at a Los Angeles County jail on an unrelated narcotics conviction, the sheriff's department said.

Whitmore said that man, John Creech, was considered a "person of interest" in the case, but has not been arrested or charged in Smith's disappearance.

MYSTERIOUS DISAPPEARANCE

It was not immediately clear if Smith and Creech were acquainted, but the missing man had met Creech's wife, Chandrika Creech, in rehab in 2009, Whitmore said.

"They had a relationship, but I'm not going to characterize what kind of relationship," he said.

Whitmore said detectives had spoken to Chandrika Creech and had served 25 to 30 search warrants in the sensational case. He said detectives had searched Creech's home and car, but declined to say if anything was taken as evidence.

An attorney for the Creeches could not be reached for comment on Thursday afternoon.

The sheriff's department said investigators were seeking public assistance in identifying anyone who may have helped move the Mercedes from an upscale Porter Ranch neighborhood of Los Angeles to the storage facility about a week after Smith went missing.

The sheriff's department did not say how they believe the Mercedes came to be in Porter Ranch - about 40 minutes by car from Oak Park, where Smith was last seen, and 20 minutes from Simi Valley, where it was ultimately found.

"We believe other people were involved in the aftermath of moving the car and moving the body," Lieutenant Dave Dolson told reporters.

When Smith drove away from his friend's home, wearing purple athletic pants belonging to one of his sons, he left behind his cellphone charger, shaving kit and other personal items, authorities say.

His disappearance made national headlines and prompted the film studio to issue a statement expressing concern.

Smith's family posted a $20,000 reward for information and pleaded with the public to help, saying the 6-foot, 6-inch former athlete with "movie star" looks should be easy to spot.

His son Evan Smith, a forward for the University of Southern California basketball team, took to Twitter to get the word out, tweeting messages such as "I will not stop until I find my father."