A medical helicopter crashed on the roof of a hospital Thursday, catching fire moments after the two people on board escaped with minor injuries, authorities said.

The pilot and passenger were in stable condition after the crash at Spectrum Health Butterworth Hospital, said Richard Breon, president and CEO of Spectrum Health.

No patients were aboard the chopper, which crashed around 11 a.m. on a helipad atop the hospital. It landed on its side and the two people got out before it caught fire, Fire Chief John VanSolkema said.

"There's not a whole lot left, but you can tell it was a helicopter," VanSolkema said.

Crash debris was found near the hospital, but there were no reports of injuries or damage on the ground. It was too soon to determine whether the building had sustained any structural damage, VanSolkema said.

The helicopter was practicing approaches at the time of the crash, Elizabeth Isham Cory, a spokeswoman for the Federal Aviation Administration in Chicago.

All surgeries at the hospital were temporarily canceled, but were expected to resume later Thursday, said spokesman Bruce Rossman. Patients were evacuated from several floors of the hospital, but were returned to their rooms later in the day. None was injured, Rossman said.

Patients awaiting discharge were being held on the first floor of the hospital until roads leading to the facility were reopened to traffic other than emergency vehicles, he said.

A backup generator restored electricity, which went out after the Aero Med helicopter crash.

Kelli Wiltjer, a student aide in a Drug Enforcement Administration office nearby, said she looked out the window as the crash happened.

"The nose of the helicopter was kind of up and it almost looked like it was turning around, and then it dropped real fast," she said.

"Pieces were flying in the air" after the impact, said Wiltjer, 23.

Spectrum Health Butterworth, located in the heart of downtown Grand Rapids, is part of the largest campus of Spectrum Health, which is a nonprofit health care system based in western Michigan.

Butterworth Hospital is the only Level 1 trauma center for the most serious patients in western Michigan. The hospital's emergency room was closed as a result of Thursday's crash, and patients in need of emergency medical treatment were sent to other area hospitals.