An "unknown vehicle" drove into a crowd in Hollywood in the early hours of Saturday, injuring 28 people, the Los Angeles Fire Department said, without providing information on the cause of the incident.

More than 100 firefighters responded to the scene in East Hollywood assisting three patients in critical condition, six in serious condition and 19 listed as fair, the Fire Department said.

An earlier report from officials had listed four to five people in "at least critical condition."

ABC News quoted a Fire Department official saying that preliminary investigations pointed to a driver losing consciousness and ramming a large crowd outside a nightclub. However, this could not be immediately verified.

The area where the incident occurred is near Hollywood landmarks including Sunset Boulevard and the Walk of Fame -- a sidewalk emblazoned with stars commemorating movie industry figures.