Toyota Motor on Monday said it had received a subpoena from a US federal grand jury requesting documents related to unintended acceleration of its vehicles and the braking system of its Prius hybrid, as its safety woes continued to grow.

According to The Wall Street Journal, the company also said it had received a “voluntary request” and a subpoena from the Los Angeles office of the US Securities and Exchange Commission for documents related to sudden unintended acceleration and the company’s disclosure polices and practices.

The automaker also said in a statement to the London Stock Exchange that it received the grand jury request on 9 February and the SEC request on 19 February, would cooperate with the investigations and was preparing its responses.

Earlier a US media report said a document claiming Toyota saved over US$100m by persuading US government regulators to agree a cheap repair for unintended acceleration problems had raised pressure on the company’s president as he arrived in Washington to face a congressional hearing.

Toyota has recalled over 8.5m vehicles globally in recent months for problems including sticky accelerators, gas pedals that can be pinned down by loose floor mats and a braking glitch affecting the dual-model braking system in hybrid models that requires a software upgrade.

Regulators believe five deaths in the US are associated with floor mats and are reviewing up to 29 other fatality reports to see if they are related to unintended acceleration, Reuters noted.

According to the news agency and other reports, a 2009 internal document turned over to lawmakers and made available on Sunday shows Toyota’s Washington DC staff trumpeting savings of over US$100m by convincing regulators to end a 2007 investigation of sudden acceleration complaints with a relatively cheap floor mat recall.

This came after the federal government upgraded an investigation into the 2007 Lexus ES350 sedan after at least 12 people were injured when the vehicle accelerated without warning.

The 2009 document seemed certain to add to the high-stakes debate about whether Toyota missed or ignored complaints about sudden acceleration in its vehicles and whether US safety regulators were tough enough, Reuters said.

US transportation secretary Ray LaHood has recently commented harshly about the automaker, initially advising owners of recalled Toyotas not to drive them (he later recanted the comment) and later promising the administration would hold the carmaker’s “feet to the fire” as safety agencies and Congress investigated the recalls.

Toyota Motor Corporation president and family scion, Akio Toyoda, grandson of the automaker’s founder, is expected to testify before a congressional committee this week – one of three so far scheduled.

Reuters noted that the automaker had been tight-lipped about Toyoda’s US visit programme, with a spokesman declining to confirm whether the president was already in the United States. Japanese media, meanwhile, reported he had arrived in Washington and television showed images of his private jet.

Analysts told the news agency Toyoda’s appearance in Washington would be a defining moment in whether and how quickly it could move beyond its safety crisis.

“Congress is doing him a favour. He can be apologetic and be contrite and take responsibility and acknowledge that there have been some stress points in growth of the company,” Jeffrey Sonnenfeld, a Yale School of Management senior associate dean and an expert on corporate leadership, said.

Toyota shares rose as much as 3% earlier on Monday, lifted by a rally in exporters after the yen slipped against the dollar, but gains slowed and the stick closed up 1.2%, Reuters said.

“Investors remain reluctant to buy up Toyota, given uncertainty over how the congressional hearings will go,” Fumiyuki Nakanishi, head of the investment information department at SMBC Friend Securities, told the news agency.

“We are likely to see more selling of Toyota shares and buying of Honda shares,” he said. Honda Motor rose 2.8%, in line with the benchmark Nikkei average.

Toyota stock has lost 19% over the past month but has steadied over the past 10 trading sessions, the report noted.

Meanwhile, Torrance, California-based Toyota Motor Sales USA on Sunday reiterated that it was conducting a full review of all its operations.

“Our first priority is the safety of our customers and to conclude otherwise on the basis of one internal presentation is wrong,” it said in a statement on its website.

It noted it had announced a “top-to-bottom quality review of all company operations, along with new quality initiatives and a renewed commitment to transparency”.

But the US Department of Transportation said the document highlighted Toyota’s slow response to the safety problems.

“Unfortunately, this document is very telling,” department spokeswoman Olivia Alair said in a statement emailed to Reuters.

Reuters also noted that Toyota had launched a publicity campaign to convince current and prospective customers that the company was addressing the problems.

Toyota Motor Sales USA general manager Bob Carter was expected to provide an update on the recall actions later on Monday, the report added.

‘Flip-flop’ Toyoda U-turns towards Congress