Three juveniles were found safe late Thursday night, but an adult has not been located as of Friday afternoon.
Oklahoma law enforcement continued to search Friday for Gary Reece, 57, with no sign of him.
The Ark City Fire Department was called out to the river around 11:30 p.m. for the water rescue after Reece didn't resurface near the Kansas-Oklahoma border. The rapid-water response boat was lowered down an embankment east of 322nd Road, Fire Chief Bobby Wolfe said, and the rescue team entered the water around 12:30 a.m. Friday.
They searched the Arkansas River until roughly 5 a.m., with Cowley County Sheriff's deputies assisting with the initial report.
Information released by officials shows Reece swimming in the river when he began struggling to stay afloat. The three juveniles tried to help, but could not reach him before he went underwater. The children were treated for exhaustion, Wolfe said.
The Ark City Fire Department called in Oklahoma rescue, but they advised they couldn't respond until morning. ACFD stayed out searching just across the state line to try and comfort the family on scene. Deputies continued the search, along with a KHP plane overhead, but the pilot reported the river was too rapid and flooded for any good observation.
After no sign of Reece, Oklahoma tagged in at the state border continuing the search throughout Friday. OHP took over the river search with assistance from the Kay County Sheriff's Office.
Oklahoma State Troopers launched two boats at the Walnut Park in Arkansas City and called in air support for overhead monitoring. A deputy near the scene said he was on standby since 8 a.m. in case they find Reece so appropriate action could be called in immediately.
A few civilian vehicles were parked at the end of 332nd Road, about six miles east of U.S. 77 Highway, presumed to be family and friends assisting with the search. They were forced to park about a mile from the Arkansas River and walk through a recently flooded path down to the sand bar where the incident took place.