There were no unusual movements or signs of trouble in the moments before two news helicopters collided while covering an auto chase, killing all four people aboard, investigators said Friday.

The National Transportation Safety Board issued a preliminary report but made no conclusions about the cause of the July 27 accident that killed the two-man crews for KTVK-TV and KNXV-TV.

Witnesses on the ground indicated that the KTVK helicopter was relatively stationary and the KNXV helicopter "was maneuvering" when the collision happened, the report said.

"There were no reports of erratic movements prior to the collision and no unusual sounds or smoke," it said.

In all, there were five news helicopters covering the pursuit, and a police chopper was also over the site of the chase, but at a lower altitude.

The preliminary report said another pilot told the NTSB the two news helicopters were "positioned a reasonable distance apart" when he first noticed them. He then glanced away and when he looked back, the news helicopters were closer together and "shortly thereafter, they impacted."

Those killed were KNXV pilot-reporter Craig Smith, 47, and cameraman Rick Krolak, 55; and KTVK pilot-reporter Scott Bowerbank, 42, and cameraman Jim Cox, 37.

The helicopters crashed and burned in a park as TV news crews covered a chase involving a man driving a truck who had fled a traffic stop. The man was driving erratically, hitting several cars, then stopped and carjacked a pickup truck after police blew out the first truck's tires.

Just before the picture broke up, Smith said, "Oh, geez!"

The accident threw debris up to a half-mile away, but no one on the ground was injured.

The man accused of leading police on the car chase, Christopher Jones, was arrested later by a SWAT team. He has been charged with unlawful flight, assaulting a police officer and auto theft. He might also be charged in connection with the helicopter deaths, police have said.