The Centers for Disease and Control and Prevention's Morbidity and Mortality Weekly Report released Thursday said clusters of raves -- large parties where people dance to music played by disc jockeys or live performances often accompanied by light shows -- in Los Angeles on New Year's Eve ended up with 13 taken to hospital emergency rooms, with three hospitalized and one in critical condition.
"Although the initial concern was possible adulteration or contamination of drugs at the rave, the investigation concluded that the Ecstasy overdose was the primary reason for the severe symptoms," the report said.
"Evidence from drug treatment databases and crime labs suggest that Ecstasy use has been steadily increasing in Los Angeles County for the last five years."
Health officials said drug overdose is a preventable death and police, fire and emergency medical services should develop prevention strategies to reduce the number of overdoses.
While raves may not reach the crowd numbers of 20,000 they used to, smaller raves do occur regularly on several cities, especially on the West Coast.
One person died and 10 others were sickened, five critically, apparently after taking tainted drugs at a May 29 rave in Daly City, Calif. The San Jose Mercury News reported police said the victims were among about 16,500 people who attended the POP 2010 The Dream festival.