A U.S. Senate panel posed questions to a new set of key players Thursday as it delves deeper into General Motors' delayed recall of millions of small cars.

The chair of the Senate subcommittee says General Motors should have fired its chief lawyer in the wake of a long-delayed recall of millions of small cars.

An internal report found GM attorneys signed settlements with the families of crash victims but didn't tell engineers or top executives about mounting problems with ignition switches. It also found that GM's legal staff acted without urgency.

GM says faulty ignition switches were responsible for at least 13 deaths. It took the company 11 years to recall the cars.

Democratic Sen. Claire McCaskill of Missouri says GM's chief counsel, Michael Milliken, should be fired.

In prepared testimony, Milliken said he didn't learn about the switch issue until February and took immediate action.

An internal investigation led by former federal prosecutor Anton Valukas — paid for by GM — showed that even as GM lawyers recommended the settlement of similar cases involving crashes where front air bags failed to deploy in Chevrolet Cobalts and Saturn Ions, they didn't alert higher-ups, including Millikin, to a potential safety issue.

Escalating scandal

Lawmakers may also question Valukas about the report's conclusion that a lone engineer, Ray DeGiorgio, was able to approve the use of a switch that didn't meet company specifications, and years later, to order a change to the switch without any senior executives at GM being aware.

Milliken, GM CEO Mary Barra and others are appearing Thursday before the subcommittee.

Barra will certainly be asked about how she's changing a corporate culture that allowed a defect with ignition switches to remain hidden from the car-buying public for 11 years. It will be Barra's second time testifying before the panel.

Also testifying will be Rodney O'Neal, the CEO and president of Delphi. His company manufactured the ignition switches. Compensation expert Kenneth Feinberg will testify about the plan he recently unveiled for compensating victims of crashes caused by the faulty switches.