An Illinois hospital says the pilot of its helicopter encountered bad weather and was trying to return to the hangar before it crashed in a field, killing the pilot and two nurses.

Rockford Memorial Hospital spokesman Wester Wuori says pilot Andy Olesen radioed to the hospital dispatch to report that he had "encountered some weather" while heading to another hospital to pick up a patient Monday night.

Olesen and flight nurses Karen Hollis and Jim Dillow died when the plane crashed about 8:30 p.m. near Rochelle, about 70 miles west of Chicago.

No patients were aboard at the time.

The Federal Aviation Administration and National Transportation Safety Board are investigating.

Wuori says the hospital bought the helicopter in 1991, and it had a "perfect safety record."