Problem reportedly found in Japan Airlines Boeing 787 jet

In this April 26, 2013 file photo, a Japan Airlines Boeing 787 plane, foreground, sits on a tarmac with others at Haneda Airport in Tokyo. A sensor problem was found Sunday, June 2, 2013 in one of the exchanged batteries for a JAL Boeing 787 jet due to bound for Beijing from Haneda but did not pose a safety risk, a Japanese broadcaster reported. (AP/Kyodo News)

A Japanese broadcaster is reporting that a sensor problem was found in one of the exchanged batteries for a Japan Airlines Boeing 787 jet. The Boeing Co. jets had been grounded for four months until their safety could be reconfirmed.

NHK TV says the problem emerged Sunday in a sensor that detects overheating in the modified version of the lithium-ion batteries used in the aircraft. The batteries were encased to prevent overheating from spreading.

The report said the sensor problem did not endanger safety.

JAL offices were closed for the weekend, and officials were not immediately available for comment.

"Dreamliner" batteries overheated on planes that were in flight in Japan and parked in a Boston airport. The jets resumed commercial flights last month at JAL and All Nippon Airways.