The KABC news chopper was flying near City Hall Wednesday around 7 p.m. when the crew felt something hit the aircraft.
"We heard a loud bang and you could feel it," says AIR7 HD reporter Chris Cristi.
The collision did not affect AIR7 HD's ability to fly, but the crew landed quickly as a precaution.
They initially thought it was a bird but after surveying the damage they now believe it was a drone.
The chopper has a one-inch gash in its horizontal stabilizer, paint is scraped off the side and there is a dent on the tail rotor blade.
The National Transportation Safety Board is investigating the incident.
LAPD patrol officers are on the alert for pieces of wreckage east of City Hall which could weigh as much as 40 pounds. Major crimes investigators are pursuing tips.
"They are looking into leads, looking for the owner and the potential remnants of that drone," said LAPD spokesman Josh Rubenstein.
It is a violation of federal law to fly a drone without a permit at 1,100 feet where it slammed the helicopter. Drone flights are also prohibited at night and above populated areas.
"There is a reason those regulations are in place," Cristi said. "Especially at night. Especially over a populated area like downtown. It could have just have easily fallen to the ground and struck somebody in the head."
Operators are required to register their drones. On many models flight data is automatically sent to the manufacturer, which is a source of information for investigators.
There are also many professional photographers who operate at night with permits.
The AIR7 HD crew says there was no clue a drone was up so high at 7 p.m. Wednesday.
"We always know that birds are a concern, even bullets over certain areas but never a drone," Cristi said. "And I think this will be on my mind as we cruise the skies from now on."