A major clean-up is underway in Rotterdam port after 220 tonnes of fuel oil leaked into the water when a tanker owned by Norwegian shipping firm Odfjell hit a jetty, puncturing its hull.

The accident happened on Saturday afternoon and released a large quantity of heavy fuel oil from the ship’s own fuel reserves into the water. The ship itself was empty and was docking to be reloaded.

‘I can’t remember a leak on this scale in the past 10 years,’ harbour master Rene de Vries told broadcaster NOS. The clean up is a top priority for the port, he said.

Volunteers have been working hard to clean up hundreds of birds which have been covered in the oil. Ships in the port are being cleaned with high pressure hoses and special pumps are being used to salvage as much of the oil as possible, NOS said.

‘We have eight special ships pumping up the old and we will keep going until it is done,’ said Wiebbe Bonsink, of Hebo maritime services. ‘A lot of the oil has already been removed so the operation is going well.’

The port authority said on Monday afternoon around 100 tonnes of oil had already been cleaned up.

Odfjell is being held responsible for the spill, which is standard in this sort of case, De Vries said. Odfjell said in a reaction that it  has started an investigation into what went wrong and deeply regrets the accident.