U.S. auto safety regulators said Thursday they upgraded an investigation of 457,455 General Motors Corp. (GM) cars and minivans after the automaker reported 1,238 customer complaints about broken steering systems.

The investigation covers 1997 model year Pontiac Grand Prix, Chevrolet Malibu and Oldsmobile Cutlass cars, 1997 Chevrolet Venture, Pontiac Trans Sport and Oldsmobile Silhouette minivans and 1998 Oldsmobile Intrigue sedans.

The U.S. National Highway Traffic Safety Administration said it had received 200 complaints from owners claiming their steering tightened or locked without warning, resulting in 14 crashes. GM's own list of complaints includes reports of an additional 14 crashes and 8 injuries.

NHTSA said it and GM were investigating the vehicles' rack-and-pinion steering unit as a possible cause. NHTSA upgraded the investigation to an engineering analysis, one step below a recall order.

The agency also said it had opened two new investigations into Ford Motor Co. (F)'s Focus. One stems from 72 complaints from owners about engines that stall due to debris in the fuel tank; six owners reported crashes from the problem. That investigation covers about 575,000 vehicles built in 2000 and 2001.

The other investigation was spurred by seven complaints that a suspension piece can break. That investigation covers Focus models built between 2000 and 2001.

NHTSA currently has six defect investigations under way involving the Focus, the seventh best-selling car in the United States through May.