The body of a Portland man who had been missing since Friday was discovered Tuesday afternoon floating in the Presumpscot River, police said.

Lt. James Sweatt said a golfer and a manager at the Riverside Golf Course spotted “something suspicious” floating in the river near the course’s 12th hole around 12:45 p.m. The Presumpscot River flows past the entire length of the 422-yard hole off Riverside Street.

Authorities were notified immediately. They were in the midst of a massive air and ground search in the area of the golf course for Robert Koch, 52, of 723 Riverside St. Koch had been missing since he left his home around 8:30 p.m. Friday.

Sweatt said police are fairly certain the dead man is Koch. A picture identification card was found in his wallet.

“The preliminary exam shows that it is Mr. Koch,” Sweatt said during a news conference Tuesday afternoon at the Portland police station.

Sweatt said that when authorities recovered the body from the river, there was no apparent evidence that the death was suspicious. An autopsy by the state Medical Examiner’s Office will determine the exact cause of death.

“At this time, his death does not appear to be suspicious, but we are not ruling that out,” Sweatt added.

In a press release Monday, Portland police called on the public for help in finding Koch, who police said suffered “from medical conditions that may have altered his mental state. Both the police department and family members are concerned for his well-being.”

Sweatt declined to provide more details about Koch’s medical condition.

Police said Koch left his home Friday night and did not return. They said he may have been spotted around 4 a.m. Saturday at the 7-Eleven convenience store at Forest Avenue and Riverside Street but were unable to confirm that sighting.

Prior to his disappearance, Koch told family members that he was going to the Riverton Trolley Park at Forest Avenue and Riverside Street. The park features a short loop trail through woods. The trolley park abuts the Presumpscot River.

Portland police started to focus their search efforts on the trolley park and golf course area Monday night after finding an article of clothing in the park that belonged to Koch.

The search was suspended Monday night but resumed Tuesday morning. The search party included several concerned family members.

Sweatt said eight game wardens, more than 10 Portland police officers, several Maine State Police officers, police canines and a Maine Forest Service helicopter were involved in Tuesday’s search.