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Illinois police are investigating two highway shootings Monday that left a woman dead and three people wounded.

The shootings on Interstate 57 in the Chicago area occurred about eight miles and six hours apart.

An Illinois State Police spokesman Tuesday declined to tell The Associated Press whether investigators believe the two shootings are connected, adding they "have come to no conclusions."

The three people traveling in one vehicle were shot while driving northbound on the interstate, near Calumet Park, at about 4 p.m. Monday, according to Illinois State Police.

A 38-year-old man was critically wounded, and two boys, 15 and 12, were hospitalized in stable condition, police said. An 8-year-old girl in the vehicle was not shot but was also hospitalized in stable condition. A stretch of the highway was closed until after 8 p.m., police said.

About two hours after that section of the interstate reopened, police responded to a crash on the northbound side of the highway, near Oak Forest, about 8 miles southwest of the location of the first shooting. When officers arrived, they discovered a 55-year-old woman in her vehicle dead from an apparent gunshot wound. Police said the victim was a U.S. Postal Service employee who had been on her way to work.

Police are asking anyone who witnessed either shooting to come forward with information.