U.S. officials and Boeing Co. are investigating whether defective batteries from the same batch caused incidents in two 787 Dreamliners that triggered the plane’s worldwide grounding, according to two people familiar with the incidents.

If that proves to be true, it could show that a flaw causing the incidents was confined to a small number of 787s rather than a systemic fault with the plane’s engineering, design or manufacturing, and could speed the resumption of flights on the jet. The people, who weren’t authorized to speak publicly, said the information is preliminary and that investigators haven’t yet ruled out other causes.

The Federal Aviation Administration, which certified the plane in 2011, ordered flights on the 787 halted until airlines can show that the plane’s lithium-ion batteries “are safe and in compliance,” according to an agency statement this week. It didn’t say how the carriers should accomplish that.

The FAA’s move, its first in 34 years to ground an entire type of plane, set off a race to find and fix whatever caused the battery-fault warning on a 787 operated by All Nippon Airways Co. and a fire on a Japan Airlines Co. jet. The two Japanese airlines have parked their two dozen 787s, almost half the global fleet, after the battery warning forced pilots of an ANA domestic flight to make an emergency landing.

“Nobody knows what the fix is because they don’t know what the problem is,” John J. Goglia, a former member of the U.S. National Transportation Safety Board, said in an interview. Accident investigative agencies in the United States. and Japan, as well as the FAA, have not yet said what started the fires.

The batteries were made by Kyoto, Japan-based GS Yuasa Corp., which has said the Dreamliner’s faults may go beyond the batteries.

Marc R. Birtel, a spokesman for Chicago-based Boeing, said he couldn’t comment on anything related to the investigation. Peter Quinlan, a spokesman for GS Battery, a unit of GS Yuasa in Roswell, Ga., declined to comment. He referred questions to Thales SA, manufacturer of the Dreamliner’s electrical power-conversion system, which includes the batteries.

Giaime Porcu, a spokesman for the company’s Civil Aerospace Division, declined to comment. Thales is based in Neuilly, France.

A flaw in a battery, such as a manufacturing defect that allowed the flammable liquid inside to leak, might trigger a fire in one battery cell that would then ignite other cells within the pack, according to tests on generic batteries conducted by the FAA.

“Anything that involves the potential for fire onboard an aircraft, you’ve got to get to the bottom of and figure out what the corrective action is, and they will,” said former FAA head Marion C. Blakey, now president of the Arlington, Va.-based Aerospace Industries Association.

“It makes all the sense in the world to address something early, figure it out and go forward,” she said. “I think all of the customers are going to be pleased that happened, even though it’s inconvenient.”

While this week’s U.S. order affects only six planes, all flown by United Continental Holdings, it led to a worldwide grounding of the 787 as the FAA’s counterparts in Japan, India and Chile ordered Dreamliners in their countries out of service.

LOT Polish Airlines SA, Ethiopian Airlines Enterprise and Qatar Airways Ltd. also said they would suspend service of 787s. LOT’s 787 was left stranded in Chicago after its maiden trans-Atlantic flight. The European Aviation Safety Agency said that it adopted the FAA directive.

The FAA last ordered an entire type of plane grounded in 1979, when it revoked certification of the Douglas DC-10 after inspections found wing damage similar to what led to a crash in Chicago that killed 271 people. The order was lifted a month later.

“We’ve become so safe in commercial aviation that the public expects perfection,” John W. McGraw, a retired FAA official who served in the agency’s safety and certification offices, said in an interview. “Because of that, the perception of a safety risk becomes even a bigger factor with a malfunction like this.”

Before Wednesday’s ANA incident, the U.S. safety board was investigating a Jan. 7 fire in Boston aboard a Japan Airlines plane that had just arrived from Tokyo. A lithium-ion battery pack in the belly of the jet ignited, and it took airport firefighters 40 minutes to extinguish the fire, according to an NTSB news release.

The battery warning aboard the ANA 787 was on a different pack located beneath the nose of the plane.

“The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes,” the FAA said in a statement.

“These conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment.”

Lithium-ion cells are more flammable than other battery technology because they hold more energy, which can create sparks and high heat if not properly discharged. The chemicals inside the battery are also flammable and, when ignited, are difficult to extinguish because they contain their own source of oxygen, Mike Sinnett, the 787 project engineer, said last week.

Boeing chose lithium-ion batteries for the 787 because they hold more energy and can be quickly recharged, Sinnett said.

In a worst-case scenario in which the batteries do burn, they are designed to do so in a way that doesn’t threaten the aircraft, Sinnett said.

If the plane is airborne, smoke is supposed to be vented out of the compartment so that it doesn’t reach the cabin, Sinnett said, and all of the battery cells can ignite without harming the jet’s ability to stay aloft.