CABAZON, Calif. (KABC) -- The three people killed after a midair collision involving two firefighting helicopters in Riverside County were identified Monday as investigators looked into the cause of the crash.
The aircraft collided around 6:30 p.m. Sunday as crews were battling a structure fire near the intersection of Broadway Street and South Ronda Avenue in Cabazon. That blaze started as a building fire that ignited nearby brush and spread to several acres before firefighters were able to get it under control.
During a news conference Monday morning, officials said a total of six aircraft were in the air responding to the fire. Two of those collided.
The first helicopter, which typically carries retardant or water, landed safely nearby after the collision. The people on board that aircraft are OK.
WATCH: NTSB provides latest details on investigation into deadly firefighting helicopter crash in Riverside County
The other chopper, which was used for observation, crashed into a hillside after the impact. The crash sparked another four-acre fire, which was eventually extinguished.
Authorities confirmed Cal Fire Division Chief Josh Bischof, Cal Fire Captain Tim Rodriguez and Tony Sousa, a contracted pilot, were killed in the crash.
The helicopter was operating on a contract basis for firefighting agencies.
"There are numerous factors that these firefighters train for year-round to be prepared for this kind of situation... They know these aircraft very well," said CalFire spokesperson Rob Roseen.
"I would like to express our deepest sympathies and sorrow to the family and coworkers of the personnel," said David Fulcher, southern region chief for Cal Fire. "This was a tragic loss for the fire service community and Cal Fire and Riverside County Fire Department."
A somber procession for the victims was held overnight. Their bodies were escorted from the crash scene to the coroner's officer in Perris.
The National Transportation Safety Board will investigate the cause of the crash between the Bell 407 helicopter and the Sikorsky S-64E helicopter.
CalFire says neither of the helicopters reported an emergency before the collision and weather conditions were normal.
MORE COVERAGE: 3 killed after firefighting chopper crashes near Cabazon
NTSB spokesman Eleazar Nepomuceno held a news briefing in Cabazon late Monday afternoon, saying a team consisting of two NTSB investigators, a Federal Aviation Administration representative and personnel from the helicopter manufacturers, Bell and Sikorsky, were gathering preliminary information on the midair collision.
"They were on a convergence flight, and they impacted," Nepomuceno said of the choppers. "Our plan is to document the wreckage before it is relocated to (a secure hangar) in Arizona."
He said a "drone team," utilizing remotely piloted unmanned aerial vehicles, would be working Tuesday to survey the crash site.
Nepomuceno emphasized that the immediate objective is to procure "perishable" evidence that will vanish once the wreckage is removed and the crash site is cleaned up.
City News Service contributed to this report.