(PORT HURON) -- The state is charging six people connected to medical marijuana businesses in St. Clair, Sanilac and Tuscola counties. The case stems from an investigation of the Blue Water Compassion Centers, which authorities say violated drug laws. Last December, authorities raided the centers in St. Clair County's Kimball Township, Tuscola County's Denmark Township, and Worth Township and Lexington in Sanilac County. Authorities also raided a greenhouse in Sanilac County's Worth Township as well as a home. The charges announced Wednesday are from the state attorney general's office. Michigan voters in 2008 approved the use of marijuana for medical reasons, but parts of the law are being challenged.