Military officials say three people are in custody after they were found with a live mortar round in their vehicle at a gate to the sprawling Pearl Harbor military base.

A base spokesman said Wednesday that he doesn’t know what the trio planned to do or where they wanted to go.

He called the mortar round “an explosive device” and “a deadly weapon.”

The Navy said the base was shut down late Tuesday to incoming and outgoing traffic while a bomb squad investigated the vehicle that appeared at the base without authorization to enter.