DETROIT (AP) — Tests at a Michigan industrial site where limestone construction aggregate recently spilled into the Detroit River turned up no indication of excessive radiation levels, a state agency reported Friday.

Staffers with the Department of Environment, Great Lakes and Energy inspected the Detroit Bulk Storage property with federal and local officials, taking radiological measurements and sampling river water just offshore in southwest Detroit, spokesman Nick Assendelft said. A drone provided aerial footage.

“Today’s testing confirmed there is no elevated radiation risk to health or the environment associated with the collapse,” the state agency said in a statement.

The company stores and provides material for road construction, according to its website. It did not respond to phone and email messages from The Associated Press.

The release happened Nov. 26, although the state agency didn’t learn about it until Wednesday, Assendelft said. The company wasn’t required to report it because the aggregate is not a hazardous material, he said.

The aggregate was piled along a seawall, part of which collapsed, he said. The cause is undetermined, although one possibility is erosion on the swollen river — part of the natural channel linking Lakes Huron and Erie, which with the other Great Lakes are experiencing the highest water levels in decades.