U.S. officials say Chinese engineers were likely given access to the wreckage of a stealth American helicopter that crashed during the raid that killed Osama bin Laden.

The officials say Pakistan's intelligence service allowed the engineers to photograph the helicopter, which contained special technology designed to allow the aircraft to elude radar.

U.S. forces involved in the May 2 raid attempted to destroy the helicopter after it crashed into a wall of the al-Qaida leader's compound in Abbotabad, but the tail section remained largely intact.

Pakistan has close ties to China, and hinted shortly after the raid that it would allow China to study the wreckage.

U.S. officials say they have discussed the issue with Pakistani counterparts, who denied showing the remains to foreign governments.

U.S. Senator John Kerry said during a trip to Islamabad two weeks after the raid that Pakistan had promised to return the wreckage to the United States. Photographs of the remains have been widely distributed on the Internet.

Pakistan sharply criticized the U.S. raid as a violation of its sovereignty, and the operation increased already high tensions between the two countries after a CIA contractor killed two Pakistanis in January.

Pakistan has also repeatedly protested suspected U.S. drone strikes targeting militants in the country's northwest tribal region.