(Bloomberg) -- An investigation into how Fiat Chrysler’s U.S.unit has been handling the recall of millions of vehiclesintensified Monday as federal officials requested more documentsfrom the automaker and scheduled a rare public hearing.

The U.S. National HighwayTraffic Safety Administration is concerned about what it saysis the mishandling of 20 separate recalls covering more than 10million vehicles, including for repairs of fatal flaws linked toair bags and fuel tanks. It was a pattern of potential violations,rather than any specific recall, that brought the unusual agencyaction, NHTSA Administrator Mark Rosekind told reporters on aconference call.

NHTSA has become more aggressive since it was lambasted byCongress for failing to be more active prior to last year’srevelation that about 2.6 million General Motors Co. cars had aknown ignition-switch defect that went unrecalled for years. ForFiat Chrysler, the agency said it has fielded complaints fromconsumers about the absence of recall notifications, the lack ofparts when people schedule repairs and “misinformation fromdealers.”

“It is not enough to identify defects,” NHTSA Administrator MarkRosekind said. “Manufacturers have to fix them.”

June deadline

Formally known as FCA US, the Auburn Hills, Michigan-based unitof Italy’s Fiat Chrysler Automobiles NV owns the Chrysler and Jeepbrands. It was given until June 1 to turn over documents about itsrecall progress and could face fines of $7,000 per day for failingto cooperate with NHTSA’s special order.

“The average completion rate for FCA US LLC recalls exceeds theindustry average and all FCA US campaigns are conducted inconsultation with NHTSA,” the company said in an e-mailedstatement. “The company will cooperate fully.”

Rosekind declined to give an industry average after the FCAstatement. He said earlier he was unhappy with the completion rateof recall repairs for a fuel tank defect on some Jeeps.

A public hearing scheduled for July 2 is a step rarely invokedby NHTSA, which usually negotiates with automakers behind thescenes over the scope of a recall, timing and potential remedies.The last time the agency had a public hearing on a recall was in2012, for a single fix by a small motorcycle importer calledWildfire Motors.

Fuel tanks

One of the FCA recalls most at issue involves the repair of 1.56million Jeep Liberty and Grand Cherokee sport-utility vehiclesbecause of a potential defect related to fuel-tank design that canlead to fires when the vehicles are rear-ended. NHTSA had said thatas of September, only 3.9 percent of those vehicles had beenrepaired.

The agency warned Fiat Chrysler Chief Executive Officer SergioMarchionne in a November letter that the company needed toaccelerate its repairs.

In the latest updates on the Jeep fuel-tank recall filed withNHTSA, 20.6 percent of the affected vehicles were repaired at theend of March. Still, the 133,791 vehicles repaired in the firstthree months of 2015 was barely more than the 126,075 repaired inthe final three months of 2014, Rosekind said.

FCA was little changed in New York trading Monday. The shareshave climbed 33 percent this year.

Back, forth

“The company and NHTSA have been going back and forth onrecalls,” said Richard Hilgert, a Morningstar Inc. analyst inChicago. “It’s just something that’s already built into theequation.”

GM went through its own fight with NHTSA last year, thoughmanaged to defy the odds of its recalls. Instead of showroombusiness tanking -- as Toyota Motor Corp.’s did during its recallcrisis about five years ago -- GM gained market share.

“The revelations about GM’s recall fiascos didn’t clobber GMsales, but GM has more models that people want,” said Erik Gordon,a business professor at the University of Michigan in Ann Arbor.“Other than Jeep, Fiat Chrysler models are not strongly preferredby most people, so Chrysler could suffer more for its allegedsins.”

Among the 20 FCA recalls cited Monday, are ones for defectivegas tanks, flawed Takata Corp. air bags, unintended ignition switchmovement, alternator failure and loss of steering control.

It’s questionable whether Chrysler is meeting its obligations toprotect the drivers from safety defects, NHTSA’s Rosekind said. Asan example, Rosekind said the agency is continuing to get reportsabout ceiling fabric fires in the Dodge Durango and Jeep GrandCherokee, even after they’ve been recalled.

FCA could be fined a maximum of $35 million for failing tocooperate, according to NHTSA’s order.

The agency fined Honda Motor Co. a record $70 million earlierthis year for two closely related violations over its handling ofTakata air-bag failures. Rosekind declined to comment on whetherthe agency would treat each of the 20 FCA recalls under review asseparate violations.

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