DETROIT - Federal investigators are examining 46 deaths they believe could be linked to faulty Firestone tires, more than double the number they had tallied last week.
The National Highway Traffic Safety Administration had received more than 270 complaints as of Monday about failing Firestone truck tires - the vast majority installed on Ford Explorer sport utility vehicles - including at least 80 injuries, spokeswoman Liz Neblett said.
The agency had recorded 193 complaints and 21 fatalities as of last week.
The surge in complaints came as an attorneys' research group said it has found at least 50 deaths and 80 injuries resulting from failures of Firestone tires, most of which had been used on Explorers. Two more major retailers - including Discount Tire, the nation's third-largest tire chain - said they had stopped selling the Firestone ATX, ATX II and Wilderness AT models.
Ford and Firestone contend the tires are safe. Ford is doing its own investigation, while Firestone has said it would give credit toward new tires for customers who wanted to exchange their current tires.
The complaints involve reports that the tread on the Firestone models peels off, sometimes at highway speeds.
The NHTSA investigation is in the preliminary stage in which the government and manufacturers exchange paperwork; Ford and Firestone, a unit of Japanese tire maker Bridgestone Corp., have until mid-August to respond.
In a letter to Ford Motor Co. on Monday, Strategic Safety, a Virginia-based research firm for plaintiffs' attorneys, repeated a demand that Ford recall the Explorer and offer replacement tires. Ford has replaced Firestone tires for free on vehicles sold in Venezuela, Ecuador, Thailand, Malaysia, Colombia and Saudi Arabia after tires failed in those countries.
''Can the American public assume that because of the greater economic effect that accompanies a large vehicle population, Ford is unwilling to offer replacement tires in the U.S.?'' Strategic Safety said.
Ford spokesman Ken Zino said he had not seen the Strategic Safety letter and could not respond. Ford chief executive Jac Nasser released a statement Friday saying the company was concerned about the situation.
''We have teams that are working around the clock. Once we know exactly what the issues are, we will act, because we feel a responsibility to our customers, for their safety and for the safety of their families,'' Nasser said.
Firestone and some other suppliers are still selling the tires and have expressed confidence in their safety. A spokeswoman for Firestone did not immediately return calls seeking comment Monday.
Most of the accidents reported to NHTSA came from states with warmer climates. Heat can affect tire tread bonding and may be associated with an increased rate of tread separation.
General Motors, Nissan, Toyota and Subaru also sell the Firestone ATX, ATX II and Wilderness AT tires as original equipment on SUVs and pickups. All have said they have received no complaints, and planned to continue using the tires.
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