At least one person opened fire in the Southern California city of San Bernardino on Wednesday and as many as 20 people were wounded, authorities said.
The San Bernardino Police Department said on Twitter that it had "confirmed 1 to 3 possible suspects" and multiple victims in the shooting. The agency called it an "active shooter" incident.
The San Bernardino Fire Department said in a tweet that it was responding to reports of 20 victims.
The Los Angeles Times reported that the shooting took place at about 11 a.m. at a social service office in San Bernardino.
A police spokeswoman told the Times that the suspects were heavily armed and possibly wearing body armor.
A spokeswoman from nearby Loma Linda Medical Center said the hospital was expecting patients momentarily. "We're all kind of on standby right now - it could be any minute," spokeswoman Briana Pastorino said.