A newsreader has tearfully confirmed her coworkers were on board a helicopter when it crashed in Los Angeles, California.

The KNBC news helicopter was covering a fatal bus accident near Chatsworth, in the city’s northwest, when it crashed between two buildings about 7pm on Tuesday, local time.

WATCH THE VIDEO ABOVE: News helicopter crash kills three in Los Angeles

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Firefighters raced to the scene to extinguish the roaring fire before declaring three people had died in the crash.

News station KNBC went to air later that night and confirmed the helicopter was the station’s NewsChopper4.

“We’ve been piecing it together here,” newsreader Colleen Williams told viewers later that day.

“We knew it was a news chopper and we lost contact with our people out there, and we’ve just received the confirmation.

“We’re going to take a couple of minutes to think about that, to process and to regroup.”

KNBC newsreader Colleen Williams has confirmed the deaths of two coworkers in a horror helicopter crash in Los Angeles. Credit: KNBC

The station later confirmed the helicopter had pilot George Marciniw and photojournalist Eliana Moren on board. The third victim, 29-year-old Edy Gutierrez Mejia, was killed on the ground.

“We are deeply saddened to share that a helicopter providing aerial news coverage for NBC4 and Telemundo 52 (NBC4’s Spanish station) was involved in a fatal accident in Los Angeles on Tuesday evening,” KNBC said.

“We extend our heartfelt condolences to the families, friends and colleagues of those who lost their lives.”

Rival news network ABC7 extended their condolences to the friends, families and coworkers of those killed in the horror crash.

The helicopter was covering a fatal bus accident when it suddenly began to descend and crashed between two buildings. Credit: 7NEWS

“To our fellow journalists at NBC4: We are competitors, yes, but always and most importantly, colleagues,” ABC7 newsreader Marc Brown told viewers.

“Your loss is a loss to all of us.

“Tonight, please know we stand with you. We grieve with you.

“May you take comfort in the memories of those you lost.”

Investigation into helicopter crash underway

The helicopter was providing a live feed of the bus crash back to the news station at the time of the crash, which has since been spread online.

Photojournalist Eliana Moren and pilot George Marciniw were confirmed to have been killed in the crash. Credit: KNBC

It shows the helicopter circling the site of the bus accident when it suddenly began to lose altitude. The live feed cuts as the helicopter was just metres above a row of buildings.

While the footage is heartbreaking, it will help investigators from the National Transportation Safety Board (NTSB) to pinpoint exactly what caused it to happen.

“That video is probably the most important evidence that we have discovered so far,” NTSB Investigator-in-Charge Fabian Salazar told reporters on Wednesday, local time.

“What we’re going to do is get a pristine copy of that recording and send it to our recorder’s lab for a sound spectrum analysis.

“Because in that recording, we are clearly hearing sounds that are consistent with the engine changing its speed.”