CONCERT ILLNESS CAUSE SOUGHT : DISTURBANCE ERUPTED AFTER SHOW HALTED.

Byline: Kevin Ainsfeld and Mary Beth Alexander Daily News Staff Writers

Police were investigating Wednesday whether one or a combination of ``designer drugs'' or legal herbal stimulants caused more than 50 young people to become violently ill at a New Year's Eve concert.

Shut down early, the concert ended in a bottle- and rock-throwing melee on the streets of downtown Los Angeles that lasted into early New Year's Day.

The celebration was halted after dozens of concertgoers fainted or complained of nausea and dizziness. Some of the stricken partygoers stopped breathing but were revived by paramedics, fire officials said.

At least one victim remained in critical condition Wednesday.

Officials at the hospitals where the revelers were treated speculated that they had taken one or a combination of substances, including the trendy designer drugs Ecstasy or gammahydroxybutyrate, known as GHB.

``We think it was (the drug) Ecstasy,'' said Adelaida De La Cerda, a spokeswoman for Los Angeles County/USC Medical Center, where four partygoers, ages 14 to 20, were treated.

Ty Kennon, spokesman for California Medical Center, where several partygoers were treated, said two of them - a young boy and a woman - apparently were sickened after taking both GHB and Ecstasy.

``I was told it was a combination of GHB and Ecstasy,'' Kennon said, explaining that both drugs can create violent reactions. ``Respiratory depression is a side effect, so it is very dangerous.''

Authorities said Ecstasy and GHB are sweeping the club scene and are passed around freely at large parties. Both of the illegal drugs can cause euphoria, then a sudden loss of consciousness, seizures or death, officials said.

GHB, which can be easily made by mixing readily available chemicals and over-the-counter remedies, has been blamed in three recent incidents in which large numbers of people collapsed.

Police said they still were investigating what caused the mass illness at the 8 p.m. concert at the Grand Olympic Auditorium, where about 10,000 young people in their teens to early 20s had gathered.

Several thousand vials of a liquid distributed by concert organizers to guests were confiscated by police, said Sgt. Don Brady of the Los Angeles Police Department's Central Division. The solution was sent to a lab for testing, he said.

``We booked a bunch of stuff from last night, but it's pending analysis. We have no idea what it is,'' Brady said.

Concert organizer Terry Cowan told reporters Tuesday night that the vials contained a legal herb stimulant.

Brady said the vials were packaged and labeled and appeared to contain what Cowan claimed they did. Although such stimulants have been known to cause symptoms similar to those suffered by the concertgoers, Brady said police have not determined it was the orange-color liquid that made everyone sick.

``At a concert, a lot of people are ingesting a lot of alcohol and other substances,'' Brady said.

Authorities said at least 20 and as many as 30 people were taken to local hospitals after falling ill about two hours after the concert started. An additional 30 or so were treated at the scene by paramedics.

Though the concert was scheduled to last till 6 a.m. Wednesday, officers began shutting the concert down soon after the arrival of fire officials, who said the crowd was much larger than the 7,600-seat auditorium could safely hold, according to police.

At least two people, including one police officer, were injured in the fracas after the concert.

Angry that police were stopping the party early, some in the crowd began throwing rocks, bottles, wooden sticks and other objects at officers.

At one point, an angry mob converged on an MTA bus, rocked it back and forth and pounded on the windows, said Officer Mike Partain, a spokesman for the Los Angeles Police Department.

At California Medical Center, Kennon said one man was treated for injuries he suffered when he was hit by a car as the crowd dispersed. The injuries were not serious, Kennon said.

The injured police officer was hit by a bottle, police said.

Brady said the concert promoters had obtained the proper permits to hold the event at the auditorium, long a popular venue for boxing matches.

The promoters were not cited, Brady said.

At least four people were arrested on suspicion of resisting arrest and of failing to disperse, and six other people were taken into custody on suspicion of selling and distributing drugs at the concert, officials said.