Update: Thursday, May 7:

AUGUSTA – A 19-year old man is missing after attempting to swim in the Walnut River on Wednesday evening.

The search has changed from a search and rescue to a recovery effort. The County is using sonar technology and a boat as they search for the missing person according to the Butler County Sherriff’s office.

"It’s gone on for years that kids come down here along the Osage Dam," Herzet said. "These kids were down here messing around, and the gentleman said he wanted to go swimming and urged the others to get in the water with him. They didn’t, but he jumped in. He went under, never came back up, and we haven’t found him yet."

Herzet said the people who were involved were 18-19 year olds from the Augusta area.

After 7 p.m. four young men were trespassing on private property along the bank of the Walnut River near Augusta and one tried to convince the others to swim in the river. Three of the four refused and one jumped in. The other three left to bring a friend to the same area.

"The water levels are up higher right now," Herzet said. "The water is rushing pretty good. The water is still cold. It’s not a good place to swim. There’s a lot of debris in the water down there. There always has been. It’s a dangerous place. This ain’t the first time we’ve been down here for rescues."

After the landowner noticed a shirt and cell phone on the bank of the river. An Augusta office responded. He saw the group of three men and a woman walking nearby and advised them they were trespassing. The men wanted to leave but the woman hesitated and then reported the missing persons to the office according to Herzet.

"[She] said, ‘I just want to tell you that there was another guy, and he jumped in the river, and the guys told me that he never came up,'" the girl said in an interview, according to Herzet. "‘So that’s where the shirt and the cell phone came from.'"

Officials then began the rescue process through the evening with help from Augusta Public Safety, Butler County Sheriff’s deputies, Butler County Water Rescue, and Butler County EMS.

"It appears that we do have a victim in the Walnut River," Herzet said. "We have not found him yet. We have done rescue on the banks. We’ve got a boat in the water."

When questioned why the three men did not report the missing person before the woman spoke up, Herzet said they were in enough trouble with trespassing and did not want to make it worse.

"It was the girl that actually spoke up," Herzet said.

Butler County officials have notified the family of the missing 19-year old.

"Hopefully, we will find him."

Original post: 11:11 p.m., Wednesday, May 6.

According to Butler County Sheriff Kelly Herzet confirmed a search is underway for a missing boy, who was a part of a group of kids who were at the Osage Street Dam. One of them told his group of friends he was going to walk across the dam and fell in according to emergency reports.

The boy has not been seen since.

The incident occurred around 7:30 p.m. We’ll update with any up-to-date information.