The GAO, the investigative arm of Congress, is doing an ongoing investigation into counterfeit military parts, since the Defense Department draws on a large global network of suppliers.

Auditors created a fake company to allow them access to Internet sites that buy and sell defense parts. They submitted requests for fictitious parts from 16 different vendors. Then they contracted with a company that authenticates components to analyze whether the parts were legitimate.

None of the 16 parts purchased last fall, from voltage regulators to an operational amplifier, were authentic. Vendors falsified information about when the product was manufactured, refurbished old parts to look like new, re-marked them to display numbers and manufacturer logos of authentic parts, or features were deficient from military standards.

A majority of the parts the GAO received came from China, auditors said.