By Jessica Mathews /

A report of a gun turned out to be a false alarm but prompted a lockdown at the GM Proving Grounds in Milford on Friday morning.

Two buildings went into lockdown before 10am after a large law enforcement presence was reported. There were said to be initial concerns of a barricaded gunman and the incident generated a lot of response on social media.

The Detroit Free Press reports that GM develops police vehicles on site and engineers were carrying fake mock-ups of police firearms when “someone apparently saw them and thought an active shooter may have been in the building and called police”.

Despite the false alarm, police were said to have responded accordingly and work resumed at the campus.