House Members on Tuesday were in the driver’s seat as they grilled executives from Toyota Motor Corp. about the automaker’s recent safety problems, and they questioned whether Toyota had cast a wide enough net in recalling millions of its vehicles for acceleration problems.

“Thousands of Toyota owners whose cars were not subject to either recall have reported to the company that their vehicle suddenly surged or accelerated to high speeds,” said Rep. Bart Stupak (D-Mich), chairman of the Energy and Commerce Subcommittee on Oversight and Investigations, during the panel’s hearing Tuesday. “Our investigation has shown that Toyota repeatedly dismissed the possibility that electronic failures could be responsible for incidents of sudden unintended acceleration.”

At Tuesday’s hearing, Stupak also blamed executives from the world’s largest carmaker for perhaps not being forthright about the full extent of the possible malfunction of its vehicles. Since October, Toyota has recalled more than 4 million cars and trucks for a variety of possible mechanical or electronic maladies.

Stupak and other lawmakers also blamed government regulators for possibly overlooking reports of suspicious acceleration in a dozen vehicles, including in the popular Prius hybrid, Camry and Corolla models.

“Toyota’s leadership has been ambiguous about whether these two recalls fully account for and address the problem of sudden unintended acceleration,” Stupak said.

Republicans were more generous in their opening statements. While supporting a review of the National Highway Traffic Safety Administration timeline, Rep. Joe Barton (Texas), the ranking member of the Energy and Commerce panel, warned his colleagues against drawing “runaway conclusions” before all the facts are at hand.

“Maybe Toyota ignored or refused to see any problem caused by the car’s electronic throttle control systems and not by floor mats or sticky pedals,” Barton said. “Maybe NHTSA, too, shares some blame for not fully considering the broader issue of unintended acceleration. … We know what we know, but there’s vastly more that we do not know yet.”