One patient at the party was coughing and not wearing a face covering, officials said. Five cases have been confirmed, while “many more” have fallen ill.
There are 66,826 confirmed cases across California, with 2,695 deaths.
A concentration of Covid cases in California has been traced back to a birthday party in Pasadena, north-east of Los Angeles.
A “large number of extended family member and friends” attended the event, which took place after the statewide stay-home order was issued on 22 March, according to the Pasadena Public Health Department. Attendees did not practice social distancing.