Armed police are still searching for the suspect in one of California’s deadliest mass shootings.
Police officers raided a white truck near the scene of the shooting, and its driver is suspected of being involved in the accident.
A gunman escaped after killing at least 10 people near Los Angeles, wounding 10 others, some critically.
California Governor Gavin Newsom described the shooting as a “horrific and cruel” act of gun violence and expressed sympathy for the victims.
The shooting took place in Monterey Park, which has a large Asian population, shortly after thousands of people gathered for a festival to celebrate the Chinese Lunar New Year.
The gunman opened fire on a crowded dance studio in the downtown area.
California authorities said at a news conference that police had searched a white van that could be “of interest” in the investigation.
It was stated at the conference that the truck driver might be a suspect. There is no information about his status. However, some reports stated that he was killed.
Police released pictures of the suspect in the shooting, but temporarily withheld his name.
And the local “ABC7” channel reported that the truck driver was found dead inside, but there was no confirmation of this information.
Los Angeles County Sheriff Robert Luna said he believed there was only one suspect in the shooting, but added that he was not ruling out the possibility of others being involved.
He also said that he did not rule out the use of more than one weapon.
Police officer Andrew Meyer said officers arrived at the scene at 22:22 local time on Saturday (06:22 GMT Sunday), finding people “running from the scene screaming”.
Police said the victims were treated inside the Star Ballroom Dance studio and in the car park outside.
Downtown Monterey Park, including West Garvey Street where the shooting took place, was decorated for the Lunar New Year celebration.
The celebration is one of the largest in California, drawing tens of thousands of people throughout the day.
Two days of festivities were planned, but officials canceled Sunday’s events after the shooting.
There is a heavy police presence in the city – which is about seven miles (11 km) east of downtown Los Angeles – and much of the area near the dance studio has been closed off.
Police are investigating the possibility that the suspect entered another dance studio about 30 minutes after the attack.
Police said a person snatched the weapon he was carrying from the suspect at the Hambra dance studio. No one was injured at that site.
“We think there is an incident that may be related,” Luna said.
Chester Chong, president of the Chinese Chamber of Commerce in Los Angeles, told the BBC the attack stunned the community.
“This shouldn’t happen,” he said, adding that he was worried about his friend, the owner of the Star Ballroom Dance studio.
An eyewitness said that three people ran into his restaurant and told him to close the door as there was a man with a machine gun in the area.
A video clip circulating on social media showed police and firefighters rushing to an area on Garvey Street and treating victims.
The attack is one of the worst mass shootings in recent California history. The deadliest incident was in 1984, when a gunman killed 21 people at a McDonald’s branch in San Ysidro, near San Diego.
White House press secretary Karen Jean-Pierre said President Joe Biden, who has ordered the FBI to support local authorities, has been briefed.
Alhambra Mayor Sacha Rene Perez said the tragedy was “painful”.
“Residents should celebrate with family, friends and loved ones, without fear of armed violence,” she added.