Officials said the FBI and the bureau of Alcohol, Tobacco, Firearms and Explosives are putting up $50,000 each. Crime Stoppers of Mid-Michigan has committed $2,000.
The reward had been $12,000.
At least 24 reports of gunfire near I-96 have been reported since mid-October. Ten of the shootings have been in Wixom in Oakland County.
In the latest confirmed shooting, a 46-year-old West Michigan man was wounded Saturday in the buttocks when a slug slammed through his driver-side door as he drove through Livingston County toward Detroit. He's the only person wounded in the string of shootings.