Michigan State Police troopers are investigating a string of heroin overdoses on the Lakeshore.

The overdoses are reported to have happened between Tuesday Nov. 8, and Wednesday, Nov. 9. One occurred in Norton Shores and the other two were in the Grand Haven area.

According to trooper reports, one overdose victim has already been released from the hospital but the other two are in critical condition.

Investigators say the heroin was sold out of the Muskegon area, however the seller has not been located yet.

The drug task force and state troopers will continue to investigate these cases.