Authorities on Friday raided a private golf tournament in Norco at which prostitutes allegedly were selling their services on the fairways.
More than 100 people were detained for questioning by Riverside County sheriff's deputies after undercover investigators saw sex taking place at the Hidden Valley Golf Club, authorities said.
Among the detainees were 10 to 15 women, as well as employees and golfers, said sheriff's spokeswoman Shelley Kennedy-Smith.
By 9 p.m., half of those detained had been released.
No arrests had yet been made, but more than 40 people were still being questioned, Smith said.
Investigators said they believe golfers had sex with prostitutes at the club at least once before. Authorities have been watching Hidden Valley for about three weeks, they said.
On Friday, the club was reserved for a private tournament and several tents were pitched on the course. Smith said investigators observed sex between golfers and women in plain sight on the fairways.
Elsewhere on the course, golf was being played, Smith said.
Detectives don't yet know if someone hired the prostitutes or the women "just came out and acted alone."
"How long this has been going on we're not sure," Smith said. "We know, based on leads, that this has occurred on at least one other occasion."
No one at the golf club could be reached for comment.
"I think it's terrible," said Barbara Carmichael, a councilwoman in Norco, which is about 40 miles east of Los Angeles.
"I told [officials] to say it was in Corona," she joked.
Among the most flabbergasted were members of the Norco Kiwanis Club, a public-service organization that meets Friday mornings at Hidden Valley.
"My wife said no more Kiwanis meetings at the club," said Dale Borgen, the group's president-elect.
Borgen said he did not see any scantily clad women, but he did notice that the club was surprisingly empty for a Friday.
"It was a shock to me," he said. "Next week's meeting ought to be interesting."