SACRAMENTO — The new fire chief in California’s capital is clamping down on misbehaving firefighters who have been caught prowling nightclubs while on duty and taking fire engines out for joyrides. Just three days after embarassed fire officials launched an investigation into what critics say is a pattern of behavior that raises questions about the management of the department, a firefighter under investigation for allegedly sexually assaulting a 24-year-old woman during a July 3 ”Porn Star Costume Ball” was placed on paid administrative leave — along with a captain and five other firemen who also attended the costume party, all but one while on duty.

”I’m terribly disappointed,” Chief Julius ”Joe” Cherry said last week, a month after taking the helm of the oldest fire department west of the Mississippi. ”In 28 years, I have not seen a case like this.” Cherry issued a directive prohibiting on-duty personnel from going to bars, nightclubs, and other social gatherings — unless summoned for an emergency or other legitimate reason. Fire engines should no longer be used for impromptu ride-alongs, the chief ordered. And guests are no longer permitted in firehouses after 9 p.m.

The local paper weighed in with an editorial suggesting that ”flaming hormones” were just the beginning of deeper problems. ”These latest incidents feel like more than just a few firefighters who need a cold shower,” the Sacramento Bee said. ”This feels like a department with serious culture and management issues.”

That point is at the crux of a lawsuit filed last year by a former firefighter, who says she was subjected to gender discrimination and sexual harassment from other firefighters at Station 6 — which has also been implicated in one of the latest investigations.

The Fire Department’s latest travails are further evidence of the department’s history of looking the other way, said attorney Wendy York, who represents the former firefighter. Officials had launched an inquiry into the firefighter’s complaints, but a year later closed the matter and took no further action.

The department, York contends, ”hasn’t taken things seriously. There needs to be a clear message that it is unacceptable.”

The latest allegations of firefighter misconduct aren’t a surprise, York said. ”The joyrides have been going on forever.”

The inquiry into misbehavior was prompted by a letter sent to fire officials and City Councilwoman Lauren Hammond, who had reportedly been critical of the department’s handling of the sexual harassment case. She declined comment until the completion of the latest investigations.

Other city officials, including Mayor Heather Fargo, have not commented publicly about the allegations of misconduct.

Sacramento has more than 500 firefighters, of which only a small portion have been implicated in possible misdeeds, said Captain Niko King, the department’s public information officer.

”Obviously, going to bars while on duty, and using fire engines for joyrides, is not considered professional and is certainly not acceptable.” He said many in the department are angry because of the recent events. ”I’ve been hearing a lot of the guys say, ‘These guys made us look so bad; I hope they get fired,’ ” King said.

The firefighters spent nearly two hours at the porn-costume party, which despite its billing, had nothing X-rated in its program, organizers said. The event, held at a hotel ballroom during the Fourth of July weekend, featured adult-video star Teri Weigel and others and drew nearly 2,000, some in risque outfits.

The firefighters arrived in uniform and in two fire vehicles. At least one of the firefighters posed for photos with other revelers. One picture depicted him with a drink in one hand, but it was not clear if any of the firefighters had consumed any alcoholic beverages.

The crew passed on a medical emergency call, which had to be assigned to another unit because they were at the party. During the event, one of the men left the party with a woman and headed for one of the parked fire trucks, where, she told investigators, he forced her to perform oral sex. She reported the encounter to the police a few hours later.

Police lacked probable cause to make an arrest, and they are awaiting a decision from the district attorney’s office, said Sergeant Justin Risley, the Police Department’s spokesman. The district attorney’s office received results of the investigation on Wednesday but has yet to decide if it will bring charges.