TAMPA, Fla. (WFLA) — A number of students fell ill on Thursday after eating “edible substances” at Horizons Academy in Bradenton, the School District of Manatee County said.

A district spokesman sent a letter to parents on Thursday, informing them of the matter. He said an undisclosed number of students received the edibles from a classmate before school began.

The Manatee County Sheriff’s Office and school district security are still working to determine whether criminal charges are warranted and if any students violated district policy.

“Parents please speak to your student about today’s incident and please encourage your student to use extreme caution before accepting or ingesting ANY substances of unknown origin while in school or anywhere. This could cause serious illness or worse,” the letter said.

Further information about the incident was not immediately available.