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OSLO (Reuters) - Two crane ships early on Tuesday began raising a submerged Norwegian navy frigate which collided with an oil tanker in November and has remained stranded off Norway’s west coast since, the armed forces said.

The accident injured eight people and caused the temporary closure of a North Sea crude export terminal, Norway’s top gas processing plant and several offshore fields.

Raising the Helge Ingstad, one of Norway’s five frigates, is expected to take five to six days and will require calm weather.

“The work must be synchronized, so the cranes must be completely stable, next to each other,” Norway’s armed forces said in a statement.

The armed forces have said they are evaluating whether it is possible to repair the 5,290 ton Helge Ingstad or whether they will need to order a replacement frigate.