Virginia Beach officials were looking yesterday for the source of three small homemade explosives found in the sand Sunday, but they emphasized that “the beaches in and around this area are safe for all activities.”

The devices were discovered about 2:30 p.m. Sunday when Chris Petersen, 5 of Clifton Va., found and threw one of them onto packed sand where it exploded. He had been playing catch with his 8-year-old sister.

Authorities closed off a section of the beach for several hours to look for more explosives and found two similar devices. One had been set off, and the other was detonated by a state police bomb squad.

A Marine was charged with the manufacture, possession and use of explosives, said arson investigators.

Authorities knew of no motive for the use of the explosives.