DETROIT (AP) -- There's no need to tell owners of recalled General Motors small cars to stop driving them, according to U.S. Transportation Secretary Anthony Foxx.
In a written response to two senators who asked for such an order, Foxx said engineers with the National Highway Traffic Safety Administration have determined it's not necessary.
GM is recalling 2.6 million small cars worldwide to replace ignition switches that suddenly can slip out of the run position and shut off the engine. That can knock out power-assisted steering and cause drivers to lose control and crash. It also disables the air bags. GM says at least 13 people have died in crashes linked to the problem. The company has admitted knowing about the problem for at least a decade, yet failing to recall the cars until this year.
The company has told owners to remove everything from their key chains, and the reduced weight will stop the switches from slipping into the "accessory" or "off" positions.
Foxx, responding to a letter from Democratic Sens. Edward Markey of Massachusetts and Richard Blumenthal of Connecticut, said NHTSA engineers have examined the geometry and physics of the key, ignition switch and steering column of the GM vehicles, and they have reviewed GM's testing data.
"NHTSA is satisfied that for now, until the permanent remedy is applied, the safety risk posed by the defect in affected vehicles is sufficiently mitigated by GM's recommended action," the letter says.
The safety agency, which is part of Foxx's department, has taken measures above and beyond normal procedures in the GM case, Foxx wrote.
The recalled cars include mainly Chevrolet Cobalts and Saturn Ions that are no longer being made. GM is in the process of shipping parts to dealers but has said it won't be done with that until October. The company is offering loaner cars to any owners with safety concerns and so far has provided about 45,000.
But Blumenthal and Markey disagree and say all the cars should be parked until the switches are replaced.
"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," the senators said in a statement Wednesday.
They also questioned why GM's initial recall notice to car owners said the ignition switches could malfunction while driving over rough terrain "regardless of additional weight on the key ring."
Both senators are members of a subcommittee that is looking into GM's actions involving the switches. NHTSA and the Justice Department are also investigating, and criminal charges are possible.
GM has said it has done 80 different tests at high speeds and on rough roads, and that with just the key in the ignition, the switches don't move out of the run position.