DETROIT – Comments from the head of the nation’s top safety regulator earlier this week suggest a potential communications breakdown between the agency and General Motors over how the auto maker would handle fixes to Chevrolet Volts on U.S. dealer lots.

The National Highway Traffic Safety Admin. discovered the potential for fire after it severely crash-tested a Volt last May and its lithium-ion battery pack sparked several weeks after the test. The regulator was able to reenact the problem again in November and opened a formal investigation.

However, no Volt battery fires have occurred in any of the more than 7,000 units currently on U.S. roads.

GM continues to sell the extended-range electric vehicle without structural enhancements meant to reduce the risk of a fire after a severe side-impact crash, leaving it up to Volt owners to decide whether they want the fix or not.

“We always knew fundamentally the Volt was safe,” says Mary Barra, senior vice president-global product development at GM.

“What we discussed was putting the decision in the hands of the customer,” she tells WardsAuto on the sidelines of an industry conference here. “If they’re not comfortable, then we’ll provide a loaner. But fundamentally, at the core of our discussions, we knew the Volt was a safe vehicle.”

NHTSA administrator David Strickland may have thought otherwise. Speaking with reporters on the eve of the North American International Auto Show, he responded with surprise at GM’s decision to keep selling Volts without the safety enhancement.

“That’s a new development,” he told reporters at the time. “I’ll have to get back with you on that.”

NHTSA officials decline to clarify Strickland’s comments. The agency typically does not comment on investigations in progress and refers a WardsAuto to its statement on Jan. 5 saying the remedy proposed GM should address the battery pack problem.

But if NHTSA believed GM would stop selling the Volt until a fix could be made, it would represent a dangerous communications breakdown between the industry and its federal safety regulator.

Two years ago, the industry and NHTSA failed to communicate closely on the unintended-acceleration issue affecting Toyota vehicles.

The problem was linked to at least one fatal crash, and Toyota ended up recalling millions of vehicles and paid record fines to NHTSA for not alerting owners sooner of potentially sticky accelerators and ill-fitting floor mats.

In the case of the Volt, “We were very transparent all the way through this,” GM North America President Mark Reuss tells WardsAuto in an interview at the auto show earlier this week, when asked about Strickland’s comments. “(NHTSA) knew everything,” he says. “There are no surprises.”

GM responded to NHTSA’s complaint by offering a loaner program to Volt owners who feared for their safety, and went as far as buying back the cars if they demanded. A handful of owners have asked for a buyback, but GM believes most will reconsider now that the auto maker has enhanced the safety of the Volt.

GM says it brought its best engineers together to find a way to enhance the safety of the Volt’s high-energy battery pack. A solution was found about four weeks later to enhance the side structure of the car to prevent damage to the unit in a severe crash.

Owners can bring their Volts to a dealer in February for the structural enhancement if they choose. Those on dealer lots will get the fix around that time, in addition to a few other minor tweaks to enhance the battery pack’s safety. The enhancement has been added to the assembly process.

Meanwhile, dealers will be selling unmodified Volts until the parts become available next month. GM had 6,183 Volts in inventory as of Jan. 1, WardsAuto data shows.

“I feel really good about the way we handled it,” Reuss says of the Volt issue. “I don’t know what we could have done more or differently.”

Barra says the Volt has received a number of top ratings from safety groups, including a “Top Safety Pick” designation from the Insurance Institute for Highway Safety. NHTSA has not issued a rating for the vehicle.

Barra says GM has conducted more than 285,000 hours of safety testing on the Volt, which is the equivalent of 25 years of real-world operation. And Volt owners have logged another 20 million miles (32 million km) of actual driving without incident.

“This was something no one could have anticipated,” Barra says of the battery pack fire.