Jared Leto and his band, just came face to face with an explosive threat: A man who panicked a crowd with a mysterious box.

Fans at a West Hollywood appearance by Jared's band, 30 Seconds to Mars, tell TMZ the man rushed the door of the building with a package in his hands.

Witnesses say the man called out Jared by name, and then said something about having explosives.

We're told a member of the band and security tackled the man until police came and arrested him.

LAPD cleared Melrose Avenue to check the box and the suspect's car -- which he had parked in the middle of the street. Cops say there was no bomb in the box -- just candy and a blender.

The man is in custody and police tell us they suspect he is mentally unstable.

Jared addressed the crowd outside after the place was evacuated, telling them the man told him "some explosives" were in the box -- and "it's official, we have the craziest fans in the world."

Leto takes control- http://www.tmz.com/videos?autoplay=true&mediaKey=5c9037bf-5f65-41d0-bf51-98cf185d9137

 

Post scare- http://www.tmz.com/videos?autoplay=true&mediaKey=740183af-d14d-40b4-89af-e1a305e7ebb2