"One of our subcontractors noticed that a network box for the shuttle had appeared to be tampered with," NASA spokeswoman Katherine Trinidad told AFP. "It is intentional damage to hardware."

Endeavour is due to be launched on August 7 from the NASA base at Cape Canaveral in Florida for a mission to the International Space Station.

The workers who discovered the damage to the computer equipment intended for Endeavour notified NASA "several days ago," Trinidad said. "There is an ongoing investigation."

Safety is a major concern in US shuttle missions after damage sustained by the Columbia craft on launching caused it to break up on re-entry in February 2003, killing all seven astronauts on board.

All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.