Two days after a medical helicopter crash took the lives of three people, federal investigators were in La Crosse County, trying to figure out what went wrong.

The victims include surgeon Darren Bean, nurse Mark Coyne and pilot Steve Lipperer.

On Monday, investigators with the National Transportation Safety Board and the Federal Aviation Administration descended on the hillside where the Madison-based medical helicopter crashed.

"We're taking coordinates for the accident site, the layout of the wreckage, and the damage in the area," says N.T.S.B. investigator Tim Sorensen.

One of the concerns clean up crews have is environmental because the helicopter was carrying so much fuel when it crashed.

"We're going to be laying out the aircraft. We'll be looking at the engine, the control systems, all the systems on the helicopter and document those," says Sorensen.

While there are still a lot of questions, Sorensen says they do know the chopper crashed soon after it left the La Crosse airport.

"By all indications it was pretty quick, within just a few minutes... exact timing we're still trying to nail that down."

A recorded conversation between the chopper's base in Madison and Gundersen Lutheran Hospital close to 20 minutes after take off was released on Monday. Sorensen says that recording may help investigators discover what happened.

La Crosse County Sheriff Steve Helgeson says the helicopter was traveling so quickly no could have survived the crash.

"The crash was a high speed crash. The estimates are that they were traveling between 140 and 150 miles per hour so there is no reason to believe that anyone would have lived past the initial crash," he says.

Sorensen says it might take months for the N.T.S.B. to finish the investigation and finally know why the medical helicopter crashed.

The company that owned the helicopter, Denver-based Air Methods, said the helicopter that crashed did not have night-vision goggles for the pilot, or a computerized crash alert system.

The N.T.S.B. recommended both the night vision goggles and the warning system in a 2006 report that suggested many fatal EMS crashes could be prevented. We also learned the chopper was filling in for the Gundersen Lutheran helicopter that was responding to a crash in Arcadia.