Toyota Motor Corp. executives debated in January the proper time to go public with mechanical problems in certain models, with one executive declaring in a Jan. 16 email, "the time to hide on this one is over," according to internal company documents viewed Wednesday.

The email was sent days before Toyota issued the last of a string of recalls covering more than eight million cars globally for reports of sudden acceleration and other safety concerns, The Wall Street Journal reported.

The Transportation Department earlier this week said it would seek a $16.4 million civil fine, the largest ever assessed against a car maker, for Toyota's failure to disclose potential safety defects as required by U.S. safety laws.

In the Jan. 16 email, Irv Miller, who then was Toyota's group vice president for environmental and public affairs, told another executive, Katsuhiko Koganei: "I hate to break this to you but WE HAVE A tendency for MECHANICAL failure in accelerator pedals of a certain manufacturer on certain models.

"We are not protecting our customers by keeping this quiet. The time to hide on this one is over," the email continued.

Mr. Miller wrote that "we need to come clean" and said he believed that top company executives were heading to Washington to discuss the matter with federal regulators. Federal regulators have said they did meet with Toyota executives in January to discuss a recall of Toyota vehicles for possible problems with sticky accelerators.

Toyota declined to comment on the email but said in a statement that it has "taken a number of important steps to improve our communications with regulators and customers on safety-related matters to ensure that this does not happen again." The contents of the email were reported earlier by the Associated Press.

Transportation Secretary Ray LaHood said in an interview Wednesday his agency isn't done with its investigation of Toyota.

"I am very skeptical of Toyota now, I really am," Mr. LaHood said. "We are not going to sleep until we have determined that Toyotas are safe to drive and that they have not hidden any information from us."