A group of preschool teachers in Los Angeles was sickened by marijuana this year after unknowingly eating pot brownies purchased from a street vendor by a fellow instructor, the U.S. Centers for Disease Control and Prevention said today.

The incident took place April 7 at an unidentified preschool and was investigated by Los Angeles police, according to the CDC report.

The preschool teacher who brought in the brownies for her colleagues told investigators that she purchased them two days earlier from a street vendor who claimed to be selling them as a church fundraiser. The unlabeled brownies cost $1.50 each and came individually in plastic wrap. The teacher did not consume any of them but said her adult son had eaten some before her bringing them to the school.

Five teachers ate one brownie each; a sixth teacher took a bite but promptly spit it out, “complaining of an unusual taste,” the CDC report said. The brownies were left in a break room.About half an hour after one of the teachers ate the brownie, the CDC report said, the preschool director and the administrator observed one instructor becoming sleepy and dizzy and suffering shortness of breath, with tingling and numbness in her face, forehead and arms.Suspicion immediately fell on the brownie.