The Pentagon stopped accepting F-35 fighter jets after discovering that the magnet used in the stealth fighter’s engine was made from unauthorized materials from China.

Pentagon spokesman Russell Gimery said: “The investigation concluded that the alloy in the engine’s lubrication pump does not comply with U.S. procurement laws that prohibit unauthorized Chinese content.”

He emphasized that “magnets do not transmit information or damage aircraft” and that “there are no risks.”

Lockheed Martin, which makes the combat aircraft, explained that the problem is related to the magnet in the F-35 fighter jet’s turbomachine, which is made by Honeywell from materials including an alloy of cobalt and samarium.

Pump manufacturer Honeywell International said it “remains committed to providing high quality products that meet or exceed all customer requirements.”

In a statement, the joint program office said that an alternative alloy source will be used in the future.

Among the components of the aircraft, there are other Chinese magnets that were rejected by former Pentagon officials.