RICHMOND -- Three teenage boys have been arrested after allegedly getting two girls drunk and raping them at Wildcat Canyon Regional Park, authorities said Thursday.

The alleged assaults occurred sometime on the evening of Nov. 29 when the three boys and two girls were in a picnic area in Alvarado Park off McBryde Avenue, said Lt. Jon King of East Bay Regional Park District police.

The suspects -- one 15-year-old and two 17-year-olds -- supplied enough alcohol to the girls for them to pass out, authorities said. The girls, ages 14 and 17, woke up the next day and realized they had been sexually assaulted, police said. They notified police and sought medical treatment, King said.

The suspects were arrested Wednesday on suspicion of rape, oral copulation, rape in concert with others and conspiracy. Their names are not being released because they are juveniles. The three suspects and the two girls are acquaintances, King said, and attend high schools in Richmond. Police would not say which schools.

The boys were booked at juvenile hall in Martinez. The incident remains under investigation and police are asking anyone with information to call the East Bay Regional Park police investigation unit at 510-690-6555.

A trial is underway this week for the suspected ringleader of a gang rape of a woman kidnapped from her Richmond neighborhood in 2008. Humberto Salvador, identified by police as a 36-year-old gang member, is alleged to have raped the woman with others in part because she is a lesbian.

In October, two men were given lengthy prison sentences for the October 2009 gang rape of a 16-year-old girl outside a Richmond High School dance. Jose Montano, 22, of Richmond, received the maximum sentence of 33 years to life while his co-defendant Marcelles Peter, 20, was sentenced to 29 years to life. Cases are pending against two other defendants in connection with the incident.

David DeBolt covers breaking news. Contact him in Richmond at 510-262-2728. Follow him at Twitter.com/daviddebolt.