MINNEAPOLIS (AP) -

Authorities are searching for a man believed to have drowned in the Mississippi River in downtown Minneapolis.

The Hennepin County sheriff's office says witnesses reported seeing a man in the river just after 10:30 a.m. Tuesday, just upstream from the Hennepin Avenue Bridge.

First responders tried to throw him a rope with a flotation device attached, but he was last seen going under water. The sheriff's office says in a statement that he's believed to have drowned.

The Water Patrol used boats to search the flood-swollen river. The Minneapolis police and fire departments and a State Patrol helicopter also joined in the search.