VANCOUVER -- Mounties are asking anyone who may have witnessed a drowning in the Slocan River Wednesday evening to come forward.

Slocan Lake RCMP say they received a call around 5:40 p.m. for a report of a person drowning in the river, which is about 1.5 kilometres northwest of Winlaw, B.C. in the Kootenays.

Police say a 35-year-old man was swimming with someone he knew when he went under and did not come back up.

"The area in which the man went under is a well-used swimming area, which is usually shallow and there are sandbars to stand on, though the water is high right now and the undercurrent is strong," police said in a statement Thursday.

The man's friend called 911 from a nearby business, and a search and rescue operation was launched. A helicopter was used to search the water around 7:40 p.m., but Mounties say because of the time of day, search and rescue crews were unable to use a boat to search for the man.

The RCMP Underwater Recovery Team and search and rescue returned Thursday morning to resume their search.

Mounties say at this point in their investigation, they don't believe criminality was involved.

"We are mindful that the area is a popular swimming spot, and a common day use area, and we believe there is a possibility there are additional witnesses who have not yet come forward. These witnesses may not have realized what they were seeing at the time," said Cpl. Jesse O'Donaghey in an emailed statement.

Anyone who was in the area and saw what happened is asked to contact RCMP.​