WASHINGTON – A top federal safety official says the government should reconsider its approval of the kind of batteries used in the Boeing 787 Dreamliner because they can explode into fires, a specter that manufacturer testing did not pick up.

National Transportation Safety Board Chairman Hersman said Thursday that Boeing's safety testing of the batteries before they won approval from the Federal Aviation Administration showed that a short-circuit in one of the battery's eight cells could be retained in that cell.

But the NTSB's investigation of a Jan. 7 battery fire in a Japan Airlines 787 parked at Boston's Logan International Airport shows the short-circuiting quickly spread to the battery's other cells, creating a cascading, uncontrolled chemical reaction that sparked the fire.