LOS ANGELES—A long-awaited museum recognizing Mexican-Americans' contribution to Southern California culture held its first official event Saturday night under clouds of controversy and protest surrounding the treatment of human remains found during the facility's construction.

Native American demonstrators with drums and tribal garb protested outside the gala celebration marking the opening of the LA Plaza de Cultura y Artes cultural center, which guests paid between $1,000 and $100,000 to attend.

A statement announcing the demonstration accused Los Angeles County officials of allowing the desecration of a historic cemetery where hundreds of people are believed to be buried.

Christina Swindall-Martinez, secretary for the Gabrieleno Band of Mission Indians, said tribe members had pleaded with museum and county officials to delay the opening until an agreement could be reached on the restoration of the cemetery and the reinterment of the remains found there.

She said members felt particularly affronted by Los Angeles County Supervisor Gloria Molina, who has long championed the project, serves on its board and was scheduled to be honored at the gala.

"Molina has the nerve to celebrate and have a party while our ancestors are in buckets and bags," she said. "She needs to show us some good faith in remedying this situation and she has not done anything like that all along the road at all."

Molina spokeswoman Roxane Marquez declined

to comment.

Several streets and sidewalks surrounding the museum, built within the city's El Pueblo historic district, were blocked to divert traffic and pedestrians from the partially outdoor event.

Swindall-Martinez said she and other protesters were nowhere near the people entering the party, but said it was more important that their message reached the public and passers-by. She said they had no intention of disrupting the festivities, only of having their message heard.

"It's just to let them know that we don't approve of this gala," she said.

Museum representative Manuel Valencia said in an email that the celebration went well.

"Everyone is celebrating the opening of LA Plaza," he wrote. "There have been no disruptions."

The dispute stems from the bones crews unearthed in October as they completed the excavation work for the project's garden. The museum is at the site of a former cemetery that had been documented as having been completely exhumed in 1848.

LA Plaza administrators insisted that the bones belonged to Christian parishioners from an adjacent church until Indian groups produced burial records showing that about two-thirds of the roughly 670 people buried in the so-called Campo Santo graveyard were Gabrielino-Tongva Indians and members of other tribes.

Museum administrators stopped work in the segment of the garden where the 118 sets of remains were found in mid-January, about a week after Indian leaders began raising concerns.

The remains were first transported to a storage facility at California State University, Los Angeles, then taken to the Los Angeles County Museum of Natural History in 15 brown paper grocery bags, according to Los Angeles County coroner's logs and emails released to the City Project, a Los Angeles-based public interest law group, under a public records request.

The coroner's documents reveal museum administrators and county officials were preoccupied with avoiding scrutiny about the remains as the museum's opening date approached.

Coroner's investigator Elissa Fleak noted on Oct. 28, when she was summoned to the site after remain were first found, that museum executive director Miguel Angel Corzo told her Molina "does not want media attention drawn to this project until its opening."

Chief Coroner Craig Harvey, meanwhile, noted in an Feb. 2 email that county officials wanted the remains taken from California State University to the museum in an unmarked van.

"I told her I had none, but offered my unmarked sedan," he wrote to coroner's director Anthony Hernandez. "If it is just about 15 bags, we should be OK in the back seat."

A message left with coroner's office was not returned.

Gabrieleno Band leaders had urged the sponsors of Saturday's gala, which includes Wal-Mart Stores Inc., BP PLC, Bank of America Corp. and Union Bank NA, to withdraw their support from the event and asked actress Eva Longoria, who is serving as the gala chairwoman, to dissociate herself from the project.

Longoria spokeswoman Liza Anderson declined to comment, as did Bank of America spokeswoman Colleen Haggerty.

BP spokesman Dean Scott said it contributed to the gala before learning about the remains' discovery in November and hoped the county, museum and tribe would be able to resolve the issue.

Union Bank Assistant Vice President Maria Avila Velazquez, the only company official to respond to the tribe, wrote to Swindall-Martinez that the company understands the tribe's concerns but also recognizes the museum's significance to Los Angeles and its Mexican-American community.

Wal-Mart did not return a call, nor did gala sponsors Accenture PLC or The Walt Disney Co.

The museum is scheduled to open to the public April 16 with an exhibit on Mexican-Americans' influence on Los Angeles culture and history since the city's founding in 1781 and a life-size recreation of 1920s-era Mexican-American businesses from the city's Main Street.