The Seminole County Sheriff's Office bomb squad responded to the Lake Mary Post Office Thursday morning after getting a report of a suspicious package that turned out to be an empty box.

Bomb squad investigators determined the post office was safe about 4 a.m., about 3 hours after the incident was reported.  Lake Mary police say a man called 911 after he walked into the 24-hour portion of the post office and spotted a box he thought was ticking.

Police say the ticking was actually coming from a vent in the ceiling near the box, which was sitting by itself. The man called police after became concerned that the package could have a bomb.

A team from the bomb squad, Lake Mary police, and Lake Mary Fire Rescue checked out the package and found it was empty. As a precaution, investigators closed off a portion of the eastbound lanes of Lake Mary Boulevard, but quickly had the road reopened.

Employees scheduled to begin work around 3 a.m. were kept off the property while the post office was shut down.

According to police, the package was addressed to a P.O. Box, and they're working to find out who left it behind. Since there was nothing inside, the investigation is not criminal.