DETROIT (AP) — General Motors CEO Mary Barra is preparing for a return trip to Capitol Hill as an internal investigation into the company's safety problems nears a close.

Barra privately told several lawmakers in Washington Wednesday that in a few weeks GM could simultaneously release an internal investigation into a deadly ignition switch problem as well as its plan to compensate victims, according to a congressional aide.

The ignition switches in older small cars such as the Chevrolet Cobalt and Saturn Ion can slip unexpectedly out of the "run" position, shutting off the engine and knocking out power steering and brakes. The switches also can disable the air bags. The defect is linked to at least 13 deaths.

Barra also told lawmakers that GM can't make replacement ignition parts fast enough for the 2.6 million small cars it has recalled. She said GM expects to catch up in July and start a campaign to persuade people to take cars to dealers for repairs, according to the aide, who asked not to be identified because the meetings were private.

Among the lawmakers Barra met with were Sen. Claire McCaskill, D-Missouri, and Dianna DeGette, D-Colorado. Both were highly critical of the chief executive last month when she testified at Senate and House hearings about GM's handling of the ignition switch problem. With victims' families looking on, Barra said she was unable to answer many questions until an internal investigation into the matter was complete.

Frustrated, lawmakers finally elicited a promise from Barra to return to testify when the GM probe was finished.

In late May or early June, she'll have answers. The automaker hired former U.S. Attorney Anton Valukas to investigate why it took so long for the company to recall the small cars. GM has promised an "unvarnished" report, and Barra told Congress last month she will take decisive action on its findings.

The company also hired compensation expert Kenneth Feinberg to negotiate settlements with crash victims. Lawyers say they have at least 400 possible cases against GM, and the settlements could cost the company billions.

Congress and Justice Department are investigating GM's slow response to the safety problem. The company has agreed to pay a $35 million fine assessed by the National Highway Traffic Safety Administration. It has admitted knowing about the problem for at least a decade, yet failing to recall the cars until this year.

GM confirmed that Barra met with the lawmakers and said in a statement Wednesday that since becoming CEO in January she has visited "to discuss issues that are important to them."