O'FALLON, Ill. (KSDK) - Two students were questioned about hazardous materials that were found in one student's home, according to O'Fallon, Ill. Police Chief John Betten.
The FBI has taken over the investigation. Information about how the material was found or what the substance was has not been released.
Earlier Wednesday, O'Fallon, Illinois Township High School was on lockdown because of a non-specific threat. The information was passed along to police.
Chief Betten said officials from Scott Air Force Base did a sweep of the school and did not find anything.
The lockdown was lifted.
Later on Wednesday Chief Betten confirmed four people have been arrested and taken to the O'Fallon Jail. He has not disclosed the reason for the arrest or who those four people are.
The FBI was at a home searching most of the day.