Channel 2's Mike Petchenik reports

FBI investigating explosive device found at Roswell park

A backpack spotted at a Roswell park contained explosive materials and was detonated on site, police and the FBI said Wednesday.

But investigators have not determined who left the bag in the woods at Vickery Creek Park, near the intersection of Riverside and Roswell roads.

A mother and daughter walking in the park spotted the backpack Tuesday and called police, an FBI spokesman told Channel 2 Action News. The Cobb County police bomb squad was called to the scene.

Inside the backpack, investigators find materials to make a bomb. The items detonated, according to police.

On Wednesday, local and federal investigators returned to the park to search for additional evidence. A heavy police presence was seen in the area Wednesday morning.

The park re-opened later Wednesday afternoon, according to police.

Support real journalism. Support local journalism. Subscribe to The Atlanta Journal-Constitution today. See offers.

Your subscription to the Atlanta Journal-Constitution funds in-depth reporting and investigations that keep you informed. Thank you for supporting real journalism.