GM ignition

Credit: Reuters/John Gress

A recalled Chevy Cobalt ignition switch is seen at Raymond Chevrolet in Antioch, Illinois, July 17, 2014.

The notice of the extension has already been sent to almost four and a half million current and prior owners of the eligible vehicles, the program, Feinberg said in a statement. An additional one month extension is being implemented 'out of an abundance of caution', he said.

Last week, a car-safety advocate urged a more active approach to finding cases of injury or death. Clarence Ditlow, executive director of the Center for Auto Safety, said in a letter to Feinberg that he should expand outreach efforts and scour federal car-safety databases for accidents in recalled vehicles to determine whether the switch was to blame for additional injuries or deaths.

The program, GM Ignition Compensation Claims Resolution Facility, which began accepting claims on Aug. 1, had received 1,851 claims for deaths and serious injuries linked to the switch as of Nov. 7.

(Reporting by Rama Venkat Raman in Bangalore; Editing by Muralikumar Anantharaman)