Toyota may pay $1 billion over 'runaway cars' although no-one has ever found a fault

Yet the cause of the crashes remains a mystery. There is a "lack of of evidence to date that the cars suffered from any mechanical or electronic defect,"said the WSJ.

The US National Highway Traffic Safety Administration never found flaws in the electronic throttle-control or control software of the cars. Operator error or floor mats trapping accelerator pedals were involved in most accidents, investigators decided.

A spokeswoman for Toyota said the car firm was cooperating fully with federal prosecutors.

"Toyota continues to cooperate with the U.S. attorney's office in this matter," said spokeswoman Julie Hamp. "And in the nearly four years since this inquiry began, we've made fundamental changes to become more responsive and customer focused and we're committed to continue to improve."

Toyota hasn't admitted wrongdoing in any of the law suits brought against the company involving unintended acceleration.

Prosecutors in Manhattan have been examining whether the company made false or incomplete disclosures to regulators about possible defects in its cars, according to people familiar with the matter.

Toyota recalled 10.2 million vehicles in the U.S. and 12.4 million vehicles world-wide for issues related to unintended acceleration. Investigators have also looked into possible mail and wire fraud violations connected to allegedly false disclosures. It is a federal crime to make false statements to a government agency.

A settlement over $1 billion would be one of the largest government fines ever extracted from a car firm, said the WSJ.

A Justice Department spokesman declined to discuss the specifics of any pending settlement.

"This is a landmark case because the auto industry has bobbed and weaved and done everything possible to avoid criminal sanctions forever," said Joan Claybrook, who led NHTSA from 1977 to 1981, told the Journal.

In February 2010, NHTSA said the agency had confirmed that five people in two incidents had died as a result of accidents involving claims of unwanted acceleration.

Toyota was fined four times over three years - a total of $66.2 million - by NHTSA for failing to report safety defects to the government in a timely manner. Toyota said in November 2013 that it had received two subpoenas each from the Securities and Exchange Commission and Manhattan federal prosecutors in February and June 2010 related to "unintended acceleration and certain financial records," according to regulatory filings.

A spokesman for the SEC declined to comment. A spokesman for NHTSA referred questions to the Justice Department who also declined to comment.

The issue gained national attention in 2009 after an off-duty California Highway Patrolman and his family were killed when their borrowed Lexus crashed off the road at around 120 miles an hour. The recording of a passenger's 911 call captured the driver's frantic efforts to stop the vehicle.

Toyota faced hundreds of lawsuits over the issue. In 2012, Toyota reached a settlement in a class-action suit, agreeing to pay $1.1 billion to car owners who alleged they had suffered economic damage when their vehicles lost value after the claims came to light.

All told, Toyota recalled 10.2 million vehicles in the U.S. and 12.4 million vehicles world-wide for issues related to unintended acceleration.

Toyota lost a wrongful-death civil case in Oklahoma last October.

The Prosecutors' settlement with Toyota, said the WSJ, is expected to include a criminal deferred prosecution agreement with the car maker, according to several people familiar with the negotiations.

"The precise terms of the agreement that is being considered with Toyota are unclear Such agreements generally place a company facing prosecution under probation for a set number of years, during which time the company has to fulfill certain compliance obligations to avoid criminal charges."