A medical helicopter carrying 1-year-old Kirstian Blockinger of Leland and heading for Children's Memorial Hospital in Chicago from Valley West Hospital in Sandwich crashed minutes before midnight Wednesday, Aurora police spokesman Sgt. Rob Wallers said.

The helicopter apparently clipped a radio tower wire before crashing and burning in a suburban forest. A snapped wire could be seen hanging from the 750-foot tower that stands across a busy road from the crash site, and authorities said engineers were evaluating its structural integrity. All four passengers died.

The helicopter was flying about 50 feet below the top of the tower when the wire was clipped. John Brannen of the National Transportation Safety Board said they were investigating whether lights on the tower were on at the time or could have been knocked out during the incident.

According to federal data, it's the sixth fatal crash involving medical helicopters this year. Among them was one in Maryland last month that also killed four people, including a patient.

Children's Memorial Hospital spokeswoman Julie Pesch said the child was being moved about 50 miles from Sandwich to Chicago after a closer hospital had no room for her there. Pesch also initially said the child was being transported to the hospital because of epileptic seizures. She later added she could not reveal the reason for the transport because of privacy rules. But Eva Blockinger, 89, said Kirstian was her great-granddaughter and told The Associated Press that the girl was often ill and suffered from seizures.

The crash of the Bell 222 helicopter run by Bolingbrook-based Air Angels Inc. is the second for the company in five years.