The U.S. Department of Transportation has "rebuffed" a decision made by two Democratic senators to advise owners of over 2.6 million recalled GM vehicles to stop driving them until repaired.

Transportation Secretary Anthony Foxx said that "such an action is not necessary at this time" in letters to Senators Edward Markey of Massachusetts and Richard Blumenthal of Connecticut, which were delivered this week.

GM recalled 2.6 million cars earlier this year for ignition switches that could turn off while the car was still moving. The recall comprises the 2005-'07 Chevrolet Cobalt, 2006-'07 Chevrolet HHR and Pontiac Solstice, 2007 Pontiac G5 and Saturn Sky and 2003-'07 Saturn Ion.

The recall has been linked to at least 13 fatalities.

Foxx confirmed that the department's National Highway Traffic Safety Administration "is satisfied that for now," until repairs are made, the safety risk posed by the ignition switch defect is mitigated by GM's recommendation that the vehicle be operated with just the key in the ignition switch with no other fobs or keys attached.

The added weight is believed to have caused the switches to turn from the "on" position to an "accessory" position that causes car engines to turn off.

It has also caused brakes and power steering not to work correctly, and airbags not to deploy in crashes.

"We remain extremely concerned that GM and NHTSA are not doing enough to convey the seriousness of this defect to owners of the affected cars, unnecessarily putting more lives at risk," said Blumenthal and Markey in a statement reacting to the agency's decision, according to Reuters.

Fox added that GM has tested the affected vehicles over a number of conditions, like potholes, angles railroad crossings, and panic stops.

The NHTSA has reviewed GM's tests and "and believes the information supports GM's position that the subject vehicles are safe to operate," as long as the ignition key isn't attached to other items, according to Reuters.

Two committees of Congress are investigating the reason why GM took so long to begin its recall despite knowing about the safety issue for over a decade.

Parts to fix defective ignition switches are available now at GM dealerships and dealers have already started making the necessary repairs.

Repairs usually take around 90 minutes, according to the automaker.

Owners with affected vehicles can receive more information by calling the GM Customer Engagement Center at 1-800-222-1012.

See Now: OnePlus 6: How Different Will It Be From OnePlus 5?