A document containing South Korea’s negotiation strategies for free trade talks with the United States on the sensitive issue of autos was found to have been leaked to the U.S. last month.

According to a government source Wednesday, the Foreign Ministry reported to the presidential office that during trade negotiations held earlier this month, the U.S. delegation was found to have detailed knowledge of Seoul’s strategies.

Afterwards, the presidential office instructed the National Intelligence Service to investigate the matter. The document included strategies on gas mileage and regulations on greenhouse gas emissions.

The intelligence agency's probe found that the document had been leaked by the Ministry of Knowledge Economy. The document, drafted by the Environment Ministry, was transferred to the Ministry of Knowledge Economy before it was given to auto industries both at home and in the U.S.