General Motors is replacing the executives in charge of communications and human resources as it struggles with a string of embarrassing recalls that have led to congressional hearings and federal investigations.

Communications chief Selim Bingol and human resources head Melissa Howell are leaving the company to pursue other interests, the company said Monday in a statement.

John Quattrone, who currently is executive director of human resources, will replace Howell, but GM has not yet named a replacement for Bingol, the statement said. The changes are effective immediately.

GM is in the midst of a crisis over safety of some of its older-model vehicles, including 2.6 million small cars worldwide that have been recalled to replace faulty ignition switches. GM says at least 13 deaths have been linked to the switch problem. Family members of those killed say the death toll is much higher.

The switches can unexpectedly slip from the "run" position to "accessory" or "off," shutting down the engine and disabling the power-assisted steering and brakes and the air bags. Without power steering, the cars become difficult to steer, and many drivers have inexplicably gone off the road or into oncoming traffic.

But GM spokesman Greg Martin said the moves are not linked to the recalls. He attributed them to CEO Mary Barra, who took over in February, making her own hires in key positions. "The changes are part of what any company expects during periods of transition, and Mary is building her own team," Martin said.

Bingol, a former head of communications for AT&T, was hired in 2010 by former CEO Ed Whitacre, who once was chief executive of the telecom giant. He stayed through the tenure of CEO Dan Akerson, who stepped down in February and was replaced by product development head Mary Barra.

GM credits Bingol with guiding the communications for the company's successful initial public stock offering in November of 2010, after the company emerged from bankruptcy protection.

Quattrone started working at GM in 1975 at the Fisher Body plant in Syracuse, N.Y. He has held several posts in HR and labor relations for the company since then. Before being promoted, he was the vice president for human resources for GM's engine and transmission operations.

Shares of GM rose 81 cents, or 2.5 percent, to $32.74 in midday trading Monday. They have fallen more than 8 percent since the first of the ignition switch recalls was announced on Feb. 13.

Also Monday, Barra promised employees on a company blog that the company's senior leadership will react quickly to tips from employees about safety problems. GM announced on Thursday a program to recognize and reward employees who speak up when they see something that could affect customer safety.

Company leaders will take action or close safety issues in a timely fashion, Barra promised in the blog.

"This program is an important step toward embedding the customer- and safety-centered culture in every aspect of our business," Barra said in the blog post.