U.S. officials are sure Pakistan allowed Chinese engineers to examine and photograph the wreckage of a super-secret helicopter that crashed during the May 1 raid on Osama bin Laden's compound. An unnamed U.S. intelligence source told the Financial Times the engineers were even allowed to take a sample of the modified Black Hawk's stealth "skin" to examine further. The machine crashed during the raid that resulted in Bin Laden's death, and the Navy SEALs who operated it used a hammer to smash its instruments and then blew it up with explosives. But part of the tail landed intact, outside the compound wall. That's what the Chinese scientists were allegedly allowed to see, before it was shipped back to the U.S. "American officials cautioned that they did not yet have definitive proof that the Chinese were allowed to visit to Abbottabad," The New York Times reported. "They said that Pakistani officials had denied that they showed the advanced helicopter technology to other foreign governments." That report cited an intelligence official who said "the American case was based mostly on intercepted conversations in which Pakistani officials discussed inviting the Chinese to the crash site." Intelligence officials are reportedly "certain" the Chinese engineers were given access to the wreckage.