OKMULGEE, Okla. (NewsNation) — Authorities are working to identify four bodies found in an Oklahoma river on Friday. Police believe the remains could be those of four men who were reported missing a week ago.

Police in Okmulgee, about 40 miles south of Tulsa, said Friday that the bodies of four males had been discovered in the Deep Fork River. They have been sent for autopsies.

Police said they’ve been searching for four friends — Mark Chastain, 32, Billy Chastain, 30, Mike Sparks, 32, and Alex Stevens, 29 — who were believed to have left a house in Okmulgee on bicycles on the evening of Oct. 9.

Where the four friends were headed remains a mystery.

Mark Chastain’s wife reported that he, Billy Chastain and Mike Sparks were missing on Monday, police said Tuesday. A few hours later, Alex Stevens’ mother reported him missing as well, police said.

The remains were found Friday afternoon in a river southwest of Okmulgee when a passerby told police they noticed something “suspicious” protruding from the water.

“Officers responded and discovered what appears to be multiple human remains in the river [but] we don’t know that this is our missing men yet,” said Okmulgee Police Chief Joe Prentice.

Even though the remains have not been positively identified, Prentice said the missing men’s families were informed of the discovery out of respect.

“If it turns out these missing men are the remains in the river, then the search will go from finding them to what’s happened to them. If it’s not them then we are right back to square one,” Prentice said.

Phone data previously suggested that the men may have ridden out of town in the opposite direction of the river, so police said they hadn’t considered the area where the river is located.

“We have more questions than answers,” said Prentice in a press conference Friday.

The Associated Press and NewsNation affiliate KFOR contributed to this report.