U.S. Coast Guard officials say they have ended their search for two teenage Michigan boys who went missing while swimming in Lake Michigan.

The Coast Guard said Thursday afternoon it had found no sign of the boys, identified by the Ottawa County sheriff's department as 14-year-old Vincent Green and 17-year-old Christopher Mimis. Both are from the Holland area.

They were among four teenage boys swimming Wednesday evening at Holland State Park when they were dragged out by strong currents and high waves. Two boys got out of the water, while boats and helicopters tried to rescue the others.

Authorities said earlier the search had become a recovery effort. Ensign Zach Hall says sheriff's officials remain on the water, and The Associated Press left a message for them.