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General Motors is recalling 619,122 of its last-generation compact cars in the U.S. because a heavy keyring or jarring can cause the ignition to switch off, according to documents posted on the National Highway Traffic Safety administration site.

The company is aware of 22 crashes and six fatalities related to the ignition switch in 2005- to 2007-model Chevrolet Cobalts and 2007-model Pontiac G5s. The two mechanically similar sedans are discontinued models.

The company reported to NHTSA that the switch may fail if a key ring is "carrying added weight or the vehicle goes off road or experiences some other jarring event." In those cases, the switch could be "moved out of the 'run' position."

Adding to the safety risk in case of a crash, the timing of the key movement could result in the air bags not going off.

Including cars sold elsewhere in North America., the total recall is 778,562.

GM told Reuters that it knows of five front-impact crashes and six fatalities in crashes where the front airbags did not deploy, though it said all were high-speed crashes where the probability of serious or fatal injuries was high in any case. It also said that alcohol use and not wearing seat belts figured in some of the cases.

Dealers will replace the ignition switch to remedy the problem, according to NHTSA, and GM urges owners to take non-essential items off of their key ring until the switch is replaced.