By Verena DobnikNEW YORK -- A rusted piece of airplane landing gear discovered wedged between a mosque and an apartment building and believed to be from one of the hijacked planes that destroyed the nearby World Trade Center on Sept. 11 has been confirmed as coming from the type of Boeing jet used in the attacks. Police said Saturday that detectives had been in contact with officials at Chicago-based Boeing Co. ( BA) who confirmed the wreckage was from a Boeing 767. Police have said the landing gear had a clearly visible Boeing identification number. The American Airlines ( AMR) and United Airlines ( UAL) planes hijacked by Islamic extremists in 2001 were Boeing 767s. Boeing spokesman John Dern said he could not confirm whether the ID matched the American Airlines plane or the United Airlines plane. Workers discovered the landing gear part on Wednesday between a luxury loft rental building and a mosque that in 2010 prompted virulent national debate about Islam and freedom of speech because it's just blocks from ground zero. On Saturday, yellow police tape blocked access to a metal door that leads to the hidden alley behind the planned Islamic community center, known as Park51. The medical examiner's office plans to search for Sept. 11 human remains in the alley. The chief medical examiner's spokeswoman, Ellen Borakove, said the area first will be tested as part of a standard health and safety evaluation for possible toxicity. She said sifting for human remains is to begin Tuesday morning. Retired fire department Deputy Chief Jim Riches, who lost his son in the terrorist attacks, visited the site on Saturday. He said the latest news left him feeling "upset." "The finding of this landing gear," he said, "just goes to show that we need federal people in here to do a comprehensive, full search of lower Manhattan to make sure that we don't get any more surprises," as happened in 2007 when body parts were discovered in nearby sewers and manhole covers.