Updated

The bodies of three tube riders were found Thursday after an apparent mishap along the Dan River in North Carolina and two more tubers were still missing, according to reports.

The Rockingham County Sheriff’s Office resumed the search Friday morning, with no timeline set for how long authorities would continue a rescue operation. 

"It’s a rescue mission until it becomes otherwise," a spokesperson told Fox News.

Four members of the total group of nine tubers were rescued and were being treated at a hospital, WFMY-TV in Greensboro, North Carolina, reported.

The four individuals remained hospitalized, but the sheriff’s office said they "should be fine." 

A search was underway for the missing tubers along the river near Eden, North Carolina, near the Virginia state line, about 36 miles north of Greensboro, WSET-TV station in Lynchburg, Virginia, reported.

The tubers who were found dead had apparently gone over a dam near Eden, authorities from the North Carolina State Highway Patrol told the station.

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The dam was believed to be operated by Duke Energy, Lt. Kevin Southard of the Rockingham County (N.C.) Sheriff’s Office told WFMY. Employees from the utility company spotted the tubers on the river around 4 p.m. and called 911, the station reported.

Authorities planned to make one more helicopter pass over the area Thursday night before calling off their search until Friday morning, authorities told WSET.

The helicopter was equipped with infrared technology to assist in the search, WFMY reported.

No information about the identities or ages of the tubers was immediately available.

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Emergency responders from Danville, Virginia, were expected to join in the search on Friday, if needed, the North Carolina authorities said, according to WSET.

Fox News' Peter Aitken contributed to this story.