Four Chinese oil company employees held hostage since June 2011, allegedly by Colombia’s FARC rebels, have been freed in southern Colombia, their embassy said Thursday.

“They released the four last night in the department of Caqueta. They are in good spirits,” said the spokesman of China’s embassy in Bogota.

The official said the identity of the kidnappers was still unknown. He confirmed that the four hostages — three engineers and a translator — are Chinese citizens.

President Juan Manuel Santos welcomed the news in a message on Twitter.

“I talked to the Chinese ambassador and want to celebrate the release of the four Chinese citizens. Kidnapping is not something that should be repeated again,” the president wrote.