AURORA, Ill. (AP) -- An investigation into a medical helicopter crash that killed a desperately ill 1-year-old girl and three crew members will include whether a radio tower's lights were on when the aircraft clipped the structure's wire and went down in a suburban Chicago field, authorities said.
Investigators also have pieces of the helicopter, including a mangled yellow-and-white rotor, to determine what happened to the Air Angels helicopter that crashed minutes before midnight Wednesday.
The crash caused so much damage to the 734-foot tower that Aurora police advised about 1,000 people who live nearby to leave their homes until engineers believe it is safe.
The helicopter was flying about 50 feet lower than the top of the tower when it hit the wire, said National Transportation Safety Board investigator John Brannen.
"I can say that when I was out here last night after the accident that the lights on the tower were not lit," Brannen said Thursday. The NTSB was investigating whether the lights could have been knocked out during the incident, he said.
The Air Angels helicopter was carrying Kirstin Blockinger to Children's Memorial Hospital in Chicago when it crashed.
Nearly a dozen members of the girl's family visited the site of the crash late Thursday afternoon, filing through tall grass to see the wreckage, one clutching a brown teddy bear and pink roses.
"We love Kirstin and celebrate her life, however short," said her grandfather Steve Ogletree.
Eva Blockinger told The Associated Press that her great-granddaughter often was ill and suffered from seizures.
"She was in and out of the hospital a lot," said Blockinger, 89, of Leland. "It was a regular occurrence."
A snapped wire hung from the tower across a busy road from where the twisted rotor blade could be seen near the field's edge. The crash site farther back was secured by yellow police tape and not visible from the road.
Aurora police Sgt. Chris Whitfield said that after engineers assessed the tower, residents within 1,000 feet of it were advised to evacuate their homes. Police said engineers will use a helicopter to make repairs starting Friday.
Air Angels CEO Jim Adams said operations at the Bolingbrook-based emergency medical transport service were being suspended until company officials can determine with federal investigators that the crash was not an event that could be repeated. Adams said he did not know how long that might take.
The crew members killed were pilot Del Waugh, 69, of Carmel, Ind.; paramedic Ronald Battiato, 41, of Peotone, Ill.; and nurse William Mann, 31, of Chicago. Waugh, a Vietnam vet who worked for Air Angels since 2006, had at least 4,000 hours of helicopter flying experience, said Michael Dermont, the company's director of business development.
Kirstin had been in the emergency room at Valley West Hospital in Sandwich on Wednesday night before it was decided she would be taken to the pediatric critical care unit at Children's Memorial Hospital.
Thursday's accident was the 11th crash this year, and the sixth fatal one involving medical helicopters nationwide, according to NTSB data.
The NTSB plans to hold a public hearing on medical helicopter crashes sometime next year to look into the recent increases in accident rates, said NTSB spokesman Terry Williams.
The Aurora crash was the second involving Air Angels helicopters since its inception in 1998. A January 2003 crash that killed a pilot was later determined to be caused by pilot error and weather. Mechanical problems were blamed for an August 2007 forced landing in which there were no injuries.