SEATTLE, Wash. -

Investigators trying to learn what caused a fiery helicopter crash near Seattle's Space Needle that killed two men on board and burned a third on the ground now have surveillance video footage that shows the aircraft taking off from a helipad.

Dennis Hogenson with the National Transportation Safety Board says Seattle police cataloged all the video footage captured by nearby businesses, pulled out the relevant bits and supplied copies to NTSB investigators on Thursday. He says lots of nearby businesses, including the Space Needle and a McDonald's restaurant, had some sort of video. He says some of that shows the KOMO-TV news helicopter taking off Tuesday. It plummeted to the street and burst into flames.

Investigators also took samples of the railing around the KOMO rooftop helipad. Hogenson says the samples will be sent to a materials lab in Washington, D.C. for analysis. At a secure hangar in Auburn, south of Seattle, the work of reconstructing the helicopter from its charred wreckage continues.

A preliminary report could be released by Monday. A final report could take as long as a year.