The Myllysilta bridge over the River Aura, which bisects the city, was closed on Saturday after being declared structurally unsound.

The bridge's central section is sagging by about one metre and its main supports are bent.

Professor Matti Ollila, who designed the 93-metre long bridge, says the sagging results from pack ice in the River Aura, which has dislodged its foundations. He suggests sawing the ice could help to stabilise the structure.

Barges will be driven under the bridge on Monday to support it in the event of a collapse. However, inspectors on Sunday said the sagging had slowed down considerably. Neither did they find any cracks in the bridge. But, they noted, the danger of collapse still existed.

The Accident Investigation Board says it will decide early this week if the incident requires a detailed examination. The board will determine whether to investigate the bridge even though no actual accident took place. Senior Investigator Kai Valonen says the damage to the bridge in Turku is exceptional.

According to preliminary estimates, the bridge will be closed for at least half a year. It may have to be completely replaced, which could take much longer. The one-way bridge opened in 1975, linking the Martti neighbourhood to central Turku. It carries some 25,000 vehicles daily.

Indoor Hockey Hall Evacuated

Meanwhile in Helsinki, a sports hall was closed on Saturday because of a threat of collapse. Rescue officials say the roof of the floor hockey hall in the Ruskeasuo district had begun to sag and tear under the weight of snow.

Forty people were safely evacuated from the building. The structure will remain closed for at least a week.

With snow accumulation at its highest level in decades in many places, there has been a string of roof collapses around Finland. For instance, in late February, two people were slightly injured when the roof of a sports hall in the southern town of Järvenpää collapsed. However officials say that ordinary houses should not be at risk.