Emergency crews rushed to the roof of New Mexico's only top-level trauma center Wednesday evening after a medical helicopter crashed after takeoff, but the three crew members aboard didn't appear to be seriously injured.

Authorities said the pilot was being checked out, and two other crew members were under observation after the crash at University of New Mexico Hospital in Albuquerque. They said didn't release the extent of their injuries, but said they were apparently not serious. No patients were aboard.

It's not immediately clear what caused the crash, but witnesses said they saw the PHI Air Medical helicopter wobble as it started to take off from the pad. It came to rest on its side, and the damaged tail section could be seen hanging over the edge of the roof.

"They were taking off and had already dropped off their patient when it happened," said hospital spokesman Billy Sparks.

Images of the scene showed the helicopter on its side with several firefighters on the roof. The area was soaked as they sprayed the tail section with water, but no flames could be seen.

Sparks said the fifth and sixth floors of the hospital were evacuated as a precaution. Authorities were working to determine if there was any structural damage to the building.

It's unclear how long the hospital's helipad will be out of service, but Sparks said other hospitals have volunteered to help take incoming patients if necessary.

University and Albuquerque police had roads around the hospital cordoned off Wednesday night as the investigation on the rooftop continued. Inside the hospital's emergency operations center, officials were preparing for a briefing for first responders Wednesday night.

The crash at the hospital, a busy area just north of the university, comes just weeks after a news helicopter crashed at a busy intersection near Seattle's Space Needle, killing both people on board. That crash prompted Seattle officials to review policies about permitting helicopter pads.