By JAY LINDSAYBOSTON (AP) â¿¿ An electrical fire filled the cabin of a Japan Airlines Boeing 787 with smoke Monday minutes after passengers disembarked following a non-stop flight from Tokyo. The Massachusetts Port Authority's fire chief, Bob Donahue, said the fire at Boston's Logan Airport began in a battery pack for the plane's auxiliary power unit, which runs the jet's electrical systems when it's not getting power from its engines. Fire crews using infrared equipment found flames in a small compartment in the plane's belly and had the fire out in about 20 minutes, he said. There was a flare-up later when a battery exploded, he added. "Something caused this battery pack to overheat, ignite," Donahue said, adding it's too soon to know the cause. The flight landed normally at about 10:15 a.m. Its 173 passengers and 11 crew members had already gotten off the jet when a mechanic spotted light smoke in the cockpit and cabin about 15 minutes later and notified Massport. "When we arrived, it was a heavy smoke, and that was in three minutes, so this was advancing," Donahue said. The mechanic was the only person on board when the fire broke out. One firefighter had skin irritation after contact with a chemical used to douse the fire, Donahue said. The 787 is Boeing's newest plane, and the first was delivered in late 2011. In November 2010, a test flight had to make an emergency landing after an in-flight electrical fire. The fire delayed flight tests for several weeks while Boeing investigated. Last month, a United Airlines 787 flying from Houston to Newark, N.J., diverted to New Orleans because of an electrical problem with a power distribution panel. No one was injured. The 787 uses two lithium ion batteries â¿¿ including one for the auxiliary power unit, according to a Boeing guide for firefighters dealing with the 787.