According to a law enforcement source quoted in the Los Angeles Times, police were responding to a shooting incident involving many casualties on Saturday night in Monterey Park, California.
The incident happened close to where a Chinese New Year event was taking place in Monterey Park at 10 p.m. (0600 GMT), according to the newspaper.
Earlier in the day, the festival had been attended by tens of thousands of people.
A city in Los Angeles county, Monterey Park is around 7 miles (11 km) from downtown Los Angeles.