Two brothers are presumed to have drowned in Oregon after their raft flipped over on a swift-moving river on Friday, authorities said after a multi-day search.

The brothers, ages 66 and 67, and a 61-year-old man were trying to cross the Clackamas River to access Austin Hot Springs when their raft overturned and sent all three men down river, the Clackamas County Sheriff’s Office said Sunday.

The 61-year-old man searched the area for the brothers but was unsuccessful.

Another group found the 61-year-old and offered to take him into town, officials said.

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Clackamas River

The two brothers ages, 66 and 67, were on a raft with a 61-year-old man when they flipped over in the Clackamas River on Friday. (Clackamas County Sheriff's Office)

When the missing brothers’ vehicle was found parked on a forest service road later that day, officials determined they were still missing and deployed a search and rescue team.

With diminishing daylight, searchers faced difficult conditions from the high and swift-moving river water. Crews continued to search overnight for the missing brothers.

searchers on Clackamas River shore

Search and rescue teams had looked for the two brothers since Friday. (Clackamas County Sheriff's Office)

Search efforts continued Saturday with more volunteers and local agencies using aircraft and drones, but the two men were still not found.

On Sunday, the sheriff's office said the 61-year-old man was the "lone survivor," with the brothers presumed to have drowned.

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The missing brothers were identified as 66-year-old Vasiliy Zagreychuk and 67-year-old Vladymir Zagreychuk, FOX12 Oregon reported.

searcher using drone near Clackamas River

Search teams used aircraft and drones to search for the missing brothers. (Clackamas County Sheriff's Office)

Following the search for the two men, the sheriff’s office warned those recreating along the Clackamas River to exercise caution due to the high river levels, fast-moving current and cold water temperatures.

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Officials also reminded the public that Austin Hot Springs is private property and closed for public use.