The memos are among thousands that a congressional committee has requested in a subpoena of Dimitrios Biller, who worked as a US lawyer for Toyota from 2003 to 2007.
Biller said the internal company documents show the firm was hiding evidence of safety defects from consumers and regulators.
|More than 8.5 million vehicles have been affected by Toyota's global safety recall [EPA]
In a document referring to important security issues, Toyota mentioned "sudden accelerations" on some of its vehicles, showing the company was aware of such problems in July of last year.
Toyota has recalled more than 8.5 million vehicles worldwide in recent months following a series of complaints and a slew of lawsuits linking vehicle flaws to 30 deaths across the US.
The problems include sticky accelerators, accelerators that can be pinned down by loose floor mats and a braking glitch affecting its hybrid models.
Akio Toyoda, the president of Toyota Motor Corp, is due to face a hearing before the House of Representatives Oversight and Government Reform Committee on Wednesday.
After initially ruling out such an appearance, he has since acknowledged that the automaker founded by his grandfather let its standards slip during fast growth over the past decade.
The panel will question Toyoda over his company's response to the safety issues.
Toyota in response to the internal memo reiterated in a statement late on Sunday that it was conducting a top-to-bottom review of all its operations.
It said its first priority has always been consumer safety and that "to conclude otherwise on the basis of one internal presentation is wrong".
"Our values have always been to put the customer first and ensure the highest levels of safety and quality," said the statement.
But the US transport department said the document highlighted Toyota's slow response to the safety problems.
"Unfortunately, this document is very telling," said Olivia Alair, a department spokeswoman, in an emailed statement.