DETROIT (AP) — General Motors is recalling almost 780,000 older-model compact cars in North America because a faulty ignition switch can shut off the engines without warning and cause crashes.

The company says six people have died in 22 crashes linked to the problem in Chevrolet Cobalts from the 2005 through 2007 model years, and Pontiac G5s from 2007.

A heavy key ring or jarring from rough roads can move the ignition switch out of the run position, cutting off the engine and electrical power, GM said in statements and documents released Thursday by the US National Highway Traffic Safety Administration. If that happens, the front air bags may not work if there’s a crash.

GM says the six fatalities occurred in five front-end crashes, all of which happened off-road and at high speeds. In each case, the ignition switch moved out of the run position, shutting off the engine and electrical power, spokesman Alan Adler said. That condition would cause the loss of power-steering assist and power-assisted brakes, he said.

Alcohol was involved in three of the fatalities, and in some cases the occupants weren’t wearing seat belts, Adler said.

Dealers will replace the ignition switch for free, but the timing of the recall hasn’t been finalised. Until the problem is fixed, GM is urging owners to remove nonessential items from key rings.

One owner complained to NHTSA in July of last year that the engine stopped several times while a 2006 Cobalt was being driven. “Lately my car has been dying while coming to a stop or going to take off,” the person wrote. “This is really scary when I pull out in busy traffic! I was almost T-Boned one day, but thank goodness I was able to restart my car in time.” T-boned refers to a crash in which the front of one vehicle hits the mid-side of another.

People who complain are not identified by the agency, and the cause of the person’s problem was not explained in the complaint.

Karl Brauer, senior analyst at Kelley Blue Book, said GM has improved quality in the years since the recalled cars were made. But, “this is another example of how potential engineering flaws from the past can come back to bite an automaker,” he said.

Just this week, GM scored well in a J D Power and Associates survey of owners on the dependability of 3-year-old cars. The Cadillac brand had the third-fewest problems per 100 vehicles, and GM had top-scoring vehicles in eight product segments.

GM’s Adler said the problem was discovered when the company got reports of crashes in which the air bags did not inflate. According to GM documents filed with NHTSA, the company knew of the problem as early as May of last year. But Adler said the recall didn’t take place until now because GM wasn’t able to pinpoint the cause until recently. He also said the rate of complaints was low and wasn’t growing.

More than 619,000 of the cars in the recall were sold in the US, with another 153,000 sold in Canada and more than 6,000 in Mexico, according to the company. All but 33,000 of the cars to be recalled are Cobalts. The Pontiac G5 is nearly identical to the Cobalt.

Shares of GM were down 39 cents, or 1.1 per cent, to $35.17 in afternoon trading.