Major trading house Mitsubishi Corp. and three other companies jointly obtained approval from the Canadian government last month to export shale gas from western Canada to Japan and other parts of Asia, sources said Monday.

The approval to export shale gas in the form of liquefied natural gas for an annual total of 24 million tons over 25 years has been given to Mitsubishi, Anglo-Dutch oil giant Royal Dutch Shell PLC, Korea Gas Corp. and China National Petroleum Corp., the sources said.

The four firms are expected to begin producing about 12 million tons per year starting around 2020, they said.