Law enforcement authorities will be on heightened alert Wednesday at Old Quarry Middle School after a student reported Tuesday that a bomb threat had been written on a bathroom wall.

The school was underwent a "soft" lockdown Tuesday afternoon after the threat was reported, Mary Gricus, assistant superintendent of Lemont-Bromberek Combined School District 113A, wrote in an email. Superintendent Susan Birkenmaier and Old Quarry Principal Bill Caron collaborated with members of the Lemont Police Department to investigate the incident, Gricus said.

The nature of the threat was not revealed until later Tuesday when Birkenmaier released a copy of a letter written by Caron to parents.