Japan's transport ministry said on Monday it has launched an investigation into the causes behind two fuel leaks on a Boeing Co 787 Dreamliner jet owned by Japan Airlines Co (JAL) <9201.T>.

Over the weekend, the JAL jet, which was undergoing checks in Japan following a fuel leak at Boston airport last week, leaked fuel during tests. Both of the leaks were due to separate valve-related problems.

On Friday, the U.S. government started a wide-ranging review of Boeing's 787 Dreamliner, citing concern over a battery that caught fire last week, also on a JAL plane, and other problems. The government and Boeing insisted the passenger jet remained safe to fly.

(Reporting by James Topham; Editing by Ryan Woo)