Dennis Hogenson with the National Safety Transportation Board confirmed Thursday that the Seattle Police Department had supplied his agency with video that shows the helicopter's lift off.
Hogeson said the video is not high quality.
"(They're going to) grab some stills from the video and try to enhance it," he said.
Investigators are reviewing a number of scenarios, including examining what role, if any, construction cranes in the area played, he said. They'll focus on the engine, the air frame, the pilot and the environment.
A crane operator was in radio contact with the pilot on a prior landing on the rooftop helipad, though there's no substantial evidence to link the cranes with the crash, Hogenson said.
Investigators also are poring over pilot, maintenance and company records, and they will recreate the crash scene to look for anomalies, he said. Wreckage from the helicopter has been moved to a secured hangar in Auburn, about 30 miles south of Seattle, where the team will lay out the pieces to determine what parts potentially are missing.
Hogenson said NTSB investigators are also looking at portions of the railing from the KOMO helipad.
"The team did identify a couple of sections of the railing that they wanted to do some analysis work on, so they did cut out those sections of railings and will be sending them to our materials lab for further analysis," he said.
It may be months before federal investigators know what caused the KOMO-TV news helicopter to hit the pavement and burst into flames Tuesday, setting three vehicles ablaze and spewing burning fuel down the street.
A preliminary report could be released at the end of this week or Monday. A final report with a cause could take up to a year.
The investigation team includes representatives from Airbus Helicopters, engine manufacturer Turbomeca, as well as the helicopter operator.
Witnesses reported hearing unusual noises coming from the aircraft as it lifted off from the helipad on top of Fisher Plaza, KOMO's headquarters, after refueling. Witnesses also reported seeing the helicopter rotate before it crashed.
"It pitched sideways. It was off balance, and you could tell right away something wasn't right," said Bo Bain, an excavation foreman at a nearby construction project who watched the aircraft take off. "The helicopter was struggling to stay up. It spun around, hit the top of the tree and landed on the street."
Seconds later, "It was just a fireball. The whole thing burst into flames," he said.
On Wednesday, people left flowers at the crash site to remember former KOMO veteran photographer Bill Strothman and pilot Gary Pfitzner. Both men were working for Helicopters Inc., which owned the Eurocopter AS350 helicopter. The aircraft was leased jointly by KOMO and KING-TV.
"If I knew I had Bill guiding me through a story, with his eyes looking through the lens, I knew my story would be better," said Denise Whitaker, a KOMO reporter and anchor.
Whitaker added that she always felt welcomed and safe when she flew with Gary Pfitzner. "He'd give me a grand tour of the city when possible," she said.
Mark Pfitzner told KOMO that his brother, Gary, put himself through flight school, loved to fly and "tried to do his best reporting for people."
News anchor and reporter Molly Shen remembered Strothman as "one of the best storytellers to have ever graced the halls of KOMO."
Richard Newman, 38, who suffered serious burns when the helicopter crashed on his car, was breathing on his own Wednesday, said Susan Gregg, a spokeswoman with Harborview Medical Center. The Seattle man remained in serious condition.
A man and a woman who were in vehicles that were struck by the helicopter were uninjured.