The Freedom Tower will be the tallest building in New York
A homeless man has found confidential blueprints for New York's new Freedom Tower dumped in a city rubbish bin.
Mike Fleming handed the documents - marked "Secure Document - Confidential" in to the New York Post newspaper.
The Freedom Tower is being built at Ground Zero, to replace the World Trade Centre towers destroyed on 9/11.
A spokeswoman apologised for the security breach and said that anyone found responsible would be liable for "serious disciplinary action".
Mr Fleming said he was concerned that the documents might fall into the wrong hands.
"I was outraged, because this is priceless," he told the New York Post.
"This could have ended up on eBay or gotten to al-Qaeda."
The blueprints reveal details of the new building's floor plans, along with the specifications of its concrete walls and its heating and ventilation systems.
Steve Yang, an architect who spoke to the New York Post, said that the plans would have been helpful for a terrorist planning an attack.
"An expert in explosives, demolition or biological weapons certainly could glean enough here to develop a game plan," he said.
However, Candace McAdams, a spokeswoman for the Port Authority of New York and New Jersey, which owns the site, said that the plans were "not very detailed" and available to anyone bidding on contracts.
The Port Authority will now conduct an inquiry to find out how the breach occurred.