Image: Timo Sipola / Yle

The Raksila swimming hall in Oulu has taken a step towards solving the mystery of a 'serial crapper' who has managed to shut the facility on four occasions in the last month by defecating in the pool.

Each time stools are seen in the water, the pool must be emptied and cleaned, with the community locked out for 5-6 hours at a stretch. It's a severe inconvenience for the locals and now Oulu has had enough. Municipal bosses have made a formal police complaint over the matter.

Pool manager Jari Leiväkangas said that the complaint was made due to repeated violations of the pool's clear and precise rules banning bowel movements in the water.

Investigators are now poring over surveillance camera footage in an effort to apprehend the mystery dumper.

"We have some suspicions about one individual," said Leiväkangas. "I can't say any more at this stage. Now the matter is being handled by the police."

The latest pool closure was the fourth within a month. It occurred last Thursday, when excrement was spotted at the deep end of the hall's biggest pool. Staff sprang into action, evacuating the area and starting a cleaning operation with which they are by now wearily familiar.

The repeated closures of the main pool are quite an inconvenience for the law-abiding swimmers of Oulu, with some 2,000 customers visiting the Raksila facility every day.