Sen. Claire McCaskill, speaking today on "This Week," did not rule out the possibility of jail time for General Motors employees who may have perpetrated a coverup at the company involving a defective ignition switch.

"I know Justice Department is taking a hard look," McCaskill, chair of the Senate committee charged with overseeing the alleged malfeasance, told ABC's Jon Karl.

Over the course of her investigation, she said, a year-old deposition emerged showing that GM knew at least by then that someone had redesigned the malfunctioning part and hid any tracks that would have revealed the change.

"And this company did nothing" to warn owners that they owned cars with the potentially deadly ignition switch, the Missouri Democrat said.

The company has recalled more than 2 million vehicles with a defective ignition switch that was replaced in 2006.

Asked whether she trusted the company's embattled new CEO, Mary Barra, McCaskill demurred, but said: "The facts are pretty clear. You don't need an investigation to understand that they had a defective switch and someone at GM in the engineering department changed that switch and didn't change the part number."

"There is no reason to keep the same part-number unless you're trying to hide the fact that you've got a defective switch out there that in fact ended up killing a number of people on our highways," McCaskill concluded.

The senator also seemed to leave open the possibility that GM may have to compensate the families of victims, even though the company received immunity from lawsuits as part of its 2009 bankruptcy filing.

"Well, I think this is a real moment of truth for General Motors," she said. "They've tried to lawyer up and play whack-a-mole with these lawsuits and terrible things have happened. Now it's time for them to come clean, be transparent and most of all make all victims whole, no matter when this deadly ignition caused heartbreak in their families."

ABC