Authorities booked four men into jail as persons of interest in the death of an unidentified man in the stadium parking lot Sunday, and released all but one Monday, saying he, too, would likely be freed soon.
None of the four has been charged, but police searched the home of one, in Independence, Mo., The Kansas City Star reported.
The investigation began Sunday afternoon after a man, in his 20s, was found in a parked sport utility vehicle by the owner. After a struggle, the man discovered in the car collapsed to the pavement and was later pronounced dead at a hospital, the newspaper said.
An autopsy was to be performed to determine his cause of death. Policed said there was no "obvious signs" of what killed him.
Police said the incident did not appear to be related to any fan rivalry involving the game between the Chiefs and the Denver Broncos.