The search resumed Wednesday for a man who went missing in the Potomac River, near Great Falls, one day ago.

A man who was with two swimmers called 911 from the shoreline of the Potomac River, south of Sandy Landing, at around 1:30 p.m. Tuesday, a spokesman for Montgomery County Fire and Rescue told WTOP.

One swimmer, in his late teens or early 20s, was able to get out of the water. But a man who’s about 25 years old is still missing, according to the spokesman.

The younger swimmer who got himself out of the river was evaluated and treated by Fairfax County Fire and Rescue at the scene.

Tuesday’s search included nine swift water boats, sonar, underwater drones and K9. The search had to be paused as evening storms rolled in.

Crews from the fire and rescue departments in Montgomery County and Fairfax County picked up the search Wednesday morning.

If the missing swimmer isn’t found, the fire department spokesman said the search would continue Thursday morning.

It is illegal to swim or wade in the Potomac River around Great Falls.

Earlier this summer, a 20-year-old and a 16-year-old died in separate incidents on the river.