A search was suspended Tuesday for a man who disappeared in the Potomac River in the Great Falls area, a stretch of scenic water­way known for its dangers as well as its beauty.

The apparent drowning would be the fourth this year in the part of the river from the falls to Chain Bridge, a section that has been called a drowning machine because of its swift current and often unseen hazards.

In the most recent incident, a 24-year-old man disappeared on Labor Day near the Virginia side of the river, opposite the Old Anglers Inn, according to Scott Graham, assistant chief in the Montgomery County fire and rescue service.

The man was with friends when he began to struggle and they lost contact with him, Graham said.

A search Monday night failed to find him, and efforts resumed Tuesday morning, Graham said. Seven hours of searching Tuesday were also unsuccessful, he said.

Graham said rescue personnel would reevaluate the situation Wednesday.

Those who died this year in the same area were a recent high school graduate out for a hike with friends, a soldier from Fort Myer and an experienced kayaker who was preparing for a white-water race.