According to a story published in the Detroit Free Press, Federal auto safety regulators have launched a probe into more than 1 million Ford Motor Co. cars and trucks over reports of tires leaking air because of bad valve stems made by a Chinese company.

Ford said that its look into the stems, used in a majority of its North American vehicles, uncovered a low rate of problems and no safety risks. But safety advocates said any threat of sudden loss of air to tires should be deemed serious enough for a recall.

The National Highway Traffic Safety Administration had already launched a separate investigation in May into 23 million replacement valve stems manufactured by Shanghai Baolong Automotive Corp. in 2006. The agency has found 4,767 complaints related to those valve stems, including one fatal crash of a 1998 Ford Explorer after a tire failure.

NHTSA’s preliminary probe into Ford vehicles covers 1,050,000 vehicles from a dozen 2007 models; company spokesman Wes Sherwood said the stems may have been used in other models not named by the agency.

The vehicles with the valve stems named by NHTSA include the Ford F-150, Mustang, Edge, Fusion, Expedition, Explorer, Focus and Escape, and the Mercury Grand Marquis, MKX, MKZ and Milan.

NHTSA said it has 37 complaints of bad valve stems from Ford vehicles; in 23 cases, the same vehicle had more than one bad stem, and in 11 instances, the air leak was severe enough to damage the tire.

None of the complaints to NHTSA in the most recent investigation allege any crashes or injuries because of the problem. Several owners said they were alerted to the problem by the vehicle’s tire-pressure warning system.