A fuel leak forced a Boeing 787 Dreamliner operated by Japan Airlines to return to the gate at Boston's Logan International Airport Tuesday, canceling its scheduled takeoff. The second mishap in as many days with the new model helped send Boeing's stock price down Tuesday in heavy trading.
The National Transportation Safety Board said it sent two additional investigators to Boston and formed investigative groups to look at airworthiness and fire and airport emergency response to Monday's electrical fire.
The leak occurred Tuesday on a different plane than the one that experienced the fire at Logan, said Richard Walsh, a Massport spokesman. That plane also was operated by Japan Airlines.
In Tuesday's incident, the plane had left the gate in preparation for takeoff on a flight to Tokyo when the fuel spill of about 40 gallons was discovered, Walsh said. No fire or injuries occurred, and the passengers were taken off, he said.
Boeing did not immediately respond to a request for comment.
Boeing's stock closed down 2.63 percent on Tuesday on volume of 20.2 million shares, the most traded since June 24, 2009. Its price was down nearly 5 percent during the last two days, Boeing's biggest two-day loss since Nov. 22-23, 2011.
In preliminary findings to Monday's fire, the NTSB said an investigator found that an auxiliary power unit battery had severe fire damage, and heat damage was found near the unit in the rear electronics bay.
It said it took 40 minutes to extinguish the fire.
The agency said smoke was noticed by a maintenance and cleaning crew on the plane, after passengers disembarked following a nonstop flight from Tokyo.
The auxiliary power unit 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, said the Massachusetts Port Authority's fire chief, Bob Donahue.
"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.
One firefighter had skin irritation after contact with the chemical used to douse the fire, Donahue said.
The 787 is Boeing's newest plane, 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. (Read More: Boeing's 787 Faces Scrutiny After Several Reports of Mishaps)
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 -- including one for the auxiliary power unit, according to a Boeing guide for firefighters dealing with the 787.
The rechargeable batteries, widely used in consumer devices, have some pilots worried because batteries being shipped as cargo are suspected to have caused or contributed to the severity of fires in cargo planes.
When Boeing proposed using the batteries in the 787, the Federal Aviation Administration issued special rules, including a requirement that they be designed to prevent overheating.
The FAA noted in its 2007 rule that, "In general, lithium ion batteries are significantly more susceptible to internal failures that can result in self-sustaining increases in temperature and pressure. ... The metallic lithium can ignite, resulting in a self-sustaining fire or explosion."
The severity of overheating is higher in larger batteries, the FAA said in the rule.
Boeing Co. spokeswoman Lori Gunter said the company was aware of the fire and was working with JAL. Boeing has delivered 49 787s, including seven to Japan Airlines. Another 799 have been ordered by airlines worldwide.