UPDATED: 2/27/14 4:38 pm ET
WASHINGTON -- The National Highway Traffic Safety Administration opened an investigation into the timeliness of General Motors' recall of faulty ignition switches on 1.37 million vehicles in the United States.
The agency said late Wednesday it will determine whether GM "properly followed legal processes and requirements for reporting U.S. recalls."
On Tuesday, GM added more than 588,000 vehicles to a recall to fix ignition switches that can inadvertently shut off engines and cause accidents. The problem has now been linked to 31 crashes and 13 front-seat deaths and sparked criticism of the company's years-long investigation of the problem.
The additional models increase the total number of vehicles recalled in the United States to 1.37 million. Overall, GM is recalling 1.6 millions vehicles with the problem worldwide.
The large recall covers 2005-2007 Chevrolet Cobalt, 2007 Pontiac G5, 2003-2007 Saturn Ion, 2006-2007 Chevrolet HHR, 2006-2007 Pontiac Solstice and 2007 Saturn Sky vehicles.
GM's Opel unit in Europe on Thursday recalled 2,300 2007 GTs, adding an eighth model to the list of vehicles subject to inspection and repair. No injuries or deaths have been reported in Europe, GM says.
A heavy key ring or jarring from rough pavement can move the ignition out of the run position, cutting off the engine. If that happens, the front air bags may not work, GM said.
But the company said in a statement: "We deeply regret the events that led to the recall and this investigation. As our detailed chronology indicates, we intend to fully cooperate with NHTSA and we welcome the opportunity to help the agency have a full understanding of the facts."
The first replacement parts should be available in early April, GM said. Affected owners will receive a letter from GM the week of March 10 informing them of the recall and reminding them to use only a single ignition key until their cars are repaired.
A second letter will say when they can contact dealers and schedule a repair, GM said.
GM previously said all the crashes occurred off-road and at high speeds, where the probability of serious or fatal injuries was high regardless of airbag deployment. Failure to wear seat belts and alcohol use also were factors in some cases, the company said.
GM says it first learned of the engine cutoff problem in 2004, around the time the 2005 Cobalt went on sale.
GM initially said on Feb. 13 that it would recall 780,000 Chevrolet Cobalts and Pontiac G5s from the 2005 through 2007 model years to inspect and repair the ignition switch.
The company filed documents with U.S. safety officials on Monday that detail the initial recall of "the ignition switch torque performance condition" in Chevrolet Cobalts, and Pontiac G5s and Pursuits.
GM engineers proposed a solution in 2005 that the company never implemented, according to the timetable. GM fixed the ignition switches in 474 cars under a service bulletin to dealers, a step short of a recall, that was issued in 2005 and updated in 2006.
NHTSA officials asked GM in 2007 about Cobalt ignition switches after discovering a fatal crash linked to airbag failure, which led to an internal company investigation. Part of the agency's new inquiry may be why the company didn't follow up with a recall at the time.
NHTSA urged owners and drivers to follow GM's recommendation to "use only the ignition key with nothing else on the key ring" when operating the vehicle and seek the permanent repair remedy from GM as soon as replacement parts are available.
Under federal regulations, once a manufacturer is aware of a safety problem it must, within five business days, inform NHTSA of its plan for a recall or face a civil fine. In GM's case, the maximum penalty could be $35 million.
Congress last year increased the maximum fines NHTSA can impose to $35 million to hold automakers more accountable after Toyota Motor Corp.'s recalls in 2010 due to sudden and unintended acceleration problems plaguing some of its models.
Toyota and Ford Motor Co. have paid the largest fines of more than $17 million for delaying recalls.
In the GM case, NHTSA said it "will monitor consumer outreach as the recall process continues and take additional appropriate action as warranted."
The agency considers the frequency of the incidents, the number of cars covered by the recall and the severity of injuries in determining how much to penalize a manufacturer, said David Strickland, NHTSA's former administrator.
"They look at the egregiousness of the facts, whether a manufacturer knew or should have known," said Strickland, who left the agency in January and is now an attorney for Venable LLP in Washington.
Sen. Edward Markey, D-Mass., citing the GM recall in a letter to NHTSA officials Wednesday, said the government's system designed to detect safety issues early is not working.
Had the system worked better, it might have saved lives, Markey said in a letter to David Friedman, the acting administrator of the safety agency.
"We need to overhaul the early-warning reporting system so that N.H.T.S.A. is not looking at auto defects through a rearview mirror," Markey said in a separate statement, The New York Times reported. "Making more information public can help prevent accidents and deadly crashes."
Markey is a member of the Senate's Commerce, Science and Transportation Committee, which oversees NHTSA.
He is asking NHTSA to release documents GM provided about fatal crashes in Maryland and Wisconsin, as well as information about how regulators evaluated the defect after they became aware of it.
Clarence Ditlow, executive director of the Center for Auto Safety, a Washington advocacy group that pushed for a wider recall, said the government's entire recall system is broken.
"GM doesn't get a get-out-of-jail-free card just because NHTSA did a sloppy job," Ditlow said.
The government's early-warning system was created under the Transportation Recall Enhancement, Accountability and Documentation Act.
Congress passed the 2000 law after a series of hearings into defects on Firestone tires on some Ford Explorer SUVs that caused multiple rollover crashes and deaths. The system requires automakers to notify NHTSA in a timely matter of possible defects that caused death or injuries.
Markey asked NHTSA to issue a new rule requiring automakers to provide the "detailed underlying documents that first alerted the manufacturer to the potential problem," The Times reported.
He said the information should also be made available on NHTSA's Web site for public access.
The agency often declines to release such information publicly because some material is confidential during an active investigation.
David Phillips, Gabe Nelson, Bloomberg and Reuters contributed to this report.