In Washington, U.S. Transportation Secretary Ray LaHood said the planes will not go back into service "until we are 1,000 percent sure that they are safe to fly."
In the latest incident, Japanese aviation safety officials said Friday high heat caused a battery on a Boeing 787 Dreamliner to char and swell, filling the aircraft with smoke and prompting an emergency landing Thursday, Asahi Shimbun reported. The All Nippon Airways plane landed at Takamatsu Airport in Shikoku.
Hideyo Kosugi, a deputy investigator-general for aircraft accidents, said all eight cells inside the battery were carbonized and swollen, and the battery weighed less than normal.
"What had been inside seems to have leaked under high temperatures," Kosugi said. "There is no doubt that over-voltage, over-current or overcharge occurred. The safety mechanisms may not have worked."
The likely cause for the smoke was a flammable electrolyte fluid that boiled inside the battery, he said.
Representatives of the U.S. National Transportation Safety Board, the U.S. Federal Aviation Administration and Boeing Co. arrived at Takamatsu Airport Friday to investigate the latest Dreamliner incident.
Japan's Transport Ministry and the U.S. Federal Aviation Administration grounded all Boeing 787s worldwide following a string of safety problems with the aircraft.
LaHood made his comment in Washington Friday just a week after saying the Dreamliner was safe, USA Today reported.
He said the plane was subsequently grounded "because we did further consultation with Boeing and there was another incident."
"Those planes aren't flying now until we have a chance to examine the batteries," LaHood said. "That seems to be where the problem is."
The secretary said it is unclear how soon the 787s can fly again.
"We just have to be patient here," he said. "What the American people want is to fly on planes that are safe, and that's what we're going to assure them of.
The problems with the 787s could be the result of the leading-edge technologies used in the aircraft, aviation industry observers told Asahi Shimbun.
The 787 is the first passenger aircraft to use lightweight, compact, large-capacity lithium-ion cell batteries, one of which overheated on the ANA flight Thursday. If recurring problems with the battery are confirmed, it can't be replaced easily with another battery, said a representative of GS Yuasa Corp., the battery manufacturer based in Kyoto.
"It would take several years to develop an alternative product, including the making of samples, lab tests and test flights," a GS Yuasa representative said.
Also Friday, Australia's Qantas Airline said it reduced its order for new Dreamliners by one aircraft to 14, the BBC reported.
The airline said it decided to cut its order before the airplanes were grounded and could order another Dreamliner at a later date. Qantas said the first aircraft is scheduled to arrive in mid-2013 for its economy carrier Jetstar.