MIAMI: Toyota shareholders incensed over a sudden drop in the Japanese automaker's stock price are heading to court with lawsuits claiming company executives deliberately misled investors and the public about the depth of accelerator problems in millions of its vehicles.

At least three proposed class-action lawsuits filed by Toyota investors say the company gave false initial assurances that the sudden acceleration problem was a simple matter of floor mats trapping gas pedals, helping prop up the stock price.

The shareholder cases are part of an avalanche of potentially costly lawsuits against Toyota Motor Corp. over the acceleration issue, including those filed by crash victims and their families and those brought by Toyota owners contending their vehicles are worth far less because of the recalls.

The investor lawsuits say Toyota spread misleading information through press releases, conference calls with stock analysts and TV interviews to assure stockholders and the public that the accelerator problem was easily fixed or might be the driver's fault.

Instead, the lawsuits contend, top Toyota executives have known for nearly a decade that faulty electronic throttle controls caused vehicles to sometimes careen wildly out of control but covered it up to protect the company's reputation for safety — and its stock price. The company has not issued any recalls involving flaws in the electronic throttles and has repeatedly denied they are the problem.

U.S-listed shares rose from just over $75 on Oct. 5, the day of the floor mat recall, to above $90 on Jan. 21, when Toyota announced another recall — over gas pedals it says can stick in certain conditions.

After that, the stock price fell, dropping 16 percent as of early March. Shares have since rebounded somewhat, closing Thursday on the New York Stock Exchange at $79.34, but some investors say the recovery did not prevent them from losing potentially millions of dollars as the stock was dropping.

Since the sticky pedal recall in late January, Toyota's total U.S. market capitalization has fallen 13 percent to $135.87 billion. In trading on the Tokyo Stock Exchange, Toyota shares also have lost nearly 17 percent of their value since Jan. 21. That's wiped out about 2.27 trillion yen ($25.1 billion) of the company's market capitalization there.

Toyota declined comment because the cases are pending in court. The company has repeatedly denied its electronic throttle controls are to blame for sudden acceleration.

In the lawsuits, the shareholders are asking a judge to certify a "class" of plaintiffs that would represent all Toyota shareholders in the U.S. who held company stock on specific dates. If Toyota is found liable, damages could easily run into the hundreds of millions or even billions of dollars.

The shareholder lawsuits are pending in federal court in California, the location of Toyota's North American headquarters.

In one of the lawsuits, Toyota stockholder Harry Stackhouse of Richboro, Pa., contends the company "misled investors by failing to disclose that there was a major design defect in Toyota's acceleration system, which could cause unintended acceleration."

"This drop removed the inflation from Toyota's securities prices, causing real economic loss to investors who had purchased securities," said Stackhouse, who said he bought 40 shares in late 2009 just as the accelerator problems became more widely known.

Stackhouse and the others filing suit — shareholders from Ohio and Tennessee_ did not return several telephone calls seeking comment. All three investors filed sworn statements that they did not buy the shares as an excuse to sue the company.

To win damages, the investors must be able to prove Toyota made misleading statements about an issue that would have a "material" effect on its bottom line, said James Cox, a Duke University law professor who specializes in corporate and securities law. And they must show Toyota had a duty to disclose the truthful information.

"They clearly win on the materiality issue. This is going to be a matter that hits Toyota square in the eye," Cox said. "But the mere fact that you didn't disclose it isn't necessarily fault. It's whether you have a duty."

John Coffee, a law professor at Columbia University, said there has to be strong evidence of fraud.

"Stupidity or gross negligence is not enough, and a defense by Toyota that they were surprised about the extent of the problem can be anticipated," Coffee said.

In one of the best-known recent auto product liability cases, Ford prevailed over investors who claimed the company made misleading statements about the safety of the popular Explorer sport utility vehicle prior to a massive tire recall prompted by a series of rollover crashes. A federal judge ruled in December 2001 that although some of the company statements amounted to "corporate puffery," Ford could not accurately foresee the impact of the recall when the statements were made.

"Companies are under no duty to disclose predictions that are not substantially certain to hold," wrote U.S. District Judge Arthur Tarnow of Detroit, whose ruling was upheld on appeal.

But some shareholder lawsuits claiming corporate wrongdoing have produced huge payouts to investors:

• In 2008, financial institutions were forced to cough up $7 billion for about 1.5 million shareholders of collapsed energy giant Enron Corp., following claims the banks and accounting firms took part in the fraud that kept Enron's stock prices artificially high.

• Former Worldcom directors, major investment banks and auditing firm Arthur Andersen paid more than $6 billion to investors in the wake of a huge fraud that sent the former telecommunications company's boss, Bernard Ebbers, to jail for 25 years.

Despite those successes for investors, Cox said Toyota would probably fight any settlement because investor class-action cases are notoriously difficult to win. In part, that's because Congress in 1995 made it more difficult for investors to dig into a company's documents to find damning evidence in the early stages of a case.

"They have to allege enough facts that management was acting purposely with reckless disregard," Cox said. "The courts give management an awful lot of discretion in disclosing a problem."

The automaker is also being sued by hundreds of Toyota owners seeking compensation for lost value of their cars and trucks in proposed class-action lawsuits likely to top $3 billion in possible damages. The company also faces a series of wrongful death and injury lawsuits from crashes linked to accelerator problems.

A hearing is scheduled next week in San Diego on whether to consolidate the dozens of Toyota owners' class-action lawsuits before a single judge. The investors' cases are separate from that proceeding.

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AP Auto Writer Dan Strumpf in New York contributed to this story.