SUDBURY -- Sudbury police say the lockdown on Sudbury Secondary School has been lifted after investigating a potential threat Wednesday afternoon.

The Rainbow District School Board says the school went into lockdown at 12:10 p.m. and Sudbury police were called to investigate after a threat against the school was communicated to a staff member.

The lockdown was lifted over an hour later, at 1:21 p.m.

A heavy police presence was seen at the school and officers say they spoke to the individuals involved.

Authorities say the threat is unsubstantiated, but will remain in the area as a precaution.

School board officials are reminding students that any comments that may undermine the safety of the school, whether in person or online, will be taken seriously.  

"Jokes are funny and there's nothing funny about threatening the safety and well-being of our community members," Greater Sudbury Police Service said in a tweet.

One parent tells CTV News that during the lockdown, their son's teacher barricaded the door and had everyone in the classroom hide in the corner.

The school board says a letter will be sent home to parents and guardians about the incident.