The Los Angeles news helicopter that crashed while covering a deadly bus accident is under investigation by the National Transportation Safety Board ... and they're sharing updates on their findings ... and TMZ is streaming live.

The NTSB is speaking to the media in just a few moments, the day after NBC4's helicopter tumbled out of the air and smashed onto a city street ... killing three people, including a reporter and her pilot.

As we've reported ... the crash went down Tuesday evening during news coverage. Shortly after the incident, anchor Colleen Williams told viewers the station had "lost contact with our people."

The three victims in the fiery Chatsworth crash have been identified ... reporter Eliana Moreno, pilot George Marciniw, and Edy Gutierrez Mejia. Marciniw had more than 3 decades of flight experience.

NBC Los Angeles and Telemundo 52 wrote in a joint statement ... "We are deeply saddened to share that a helicopter providing aerial news coverage for NBC4 and Telemundo 52 was involved in a fatal accident in Los Angeles on Tuesday evening. We extend our heartfelt condolences to the families, friends and colleagues of those who lost their lives."

Dispatch audio from the crash revealed the frantic response as authorities rushed to help the people in the downed helicopter.