Authorities say three suburban Detroit teachers got sick after eating marijuana-laced brownies put out in a school lounge. 

Oakland County sheriff's officials said Friday that deputies were called Wednesday to Spring Mills Elementary School in Highland Township on a tainted food complaint.  A teacher became ill the day before and later tested positive for marijuana at a hospital. 

Police say two other teachers felt sick but didn't seek medical treatment. 

The deputies recovered the remaining brownies.  Tests revealed they contained the active ingredient in marijuana. 

Huron Valley Schools officials say they are working with law enforcement to determine who brought the brownies to school. 

District officials say they don't know whether they were put out intentionally or brought by mistake.