INDIANAPOLIS — Investigators have found no evidence that a recreational vehicle produced the carbon monoxide fumes that killed an Illinois man and sickened other family members outside the Indianapolis Motor Speedway.

The RV the family was staying in did not have its engine or a generator running. Others nearby did, and investigators said they believe their emissions might have been pulled in through an open vent.

Speedway, Ind., police Lt. Trent Theobald said there was no indication of wrongdoing. He said Speedway firefighters handled the investigation.

Michael Thies, 43, of Ruma, Ill., was pronounced dead after he and three family members were found unconscious in an RV before Sunday's Indy 500. Their RV was among several parked close together in a lot across the street from the track.

Other family members included in-laws Debrah Buss, 53, who was listed in good condition Wednesday at Wishard Memorial Hospital; and Fred Buss, 61, of Oakdale, Ill., who was in serious condition in intensive care.

No condition was available for the fourth family member, Charles Buss, 69, of Marissa, Ill.