Defective switches built in Delphi's Mexico facility; parts caught before installation in customer vehicles.

General Motors has reportedly identified hundreds of defective ignition-switch kits produced by supplier Delphi.

The parts were built in Mexico and destined for some of the millions of vehicles included in GM's ignition-switch recall. More than 500 kits are said to have included components with broken tabs, though the problem was spotted before any were installed in customer vehicles.

The tabs may have affected the anti-theft systems, but would not have been considered a safety issue, GM spokesman Alan Adler told The Detroit News.

The automaker has been under pressure to hasten production of replacement parts for the recalled vehicles, most of which remain unfixed. The best-case timeline suggests all of the replacement parts will not be installed until October.

Delphi is said to be implementing a visual-inspection process on its production line to catch any additional problems before the parts are sent to dealers for installation in recalled vehicles.