(AP) - Congressman Peter King's officewas briefly sealed off Wednesday after receiving a hand-letteredenvelope marked "ammonium nitrate." But the Seaford Republican says he thinks somebody droppedsomething off by mistake and didn't realize the possibleconsequences. A man dropped off an envelope, addressed to King's congressionaloffice, around 3 p.m. The envelope also bore the words 'ammoniumnitrate,' prompting a concerned staffer to don rubber gloves, putit in a trash can, and call the Capitol police. King has been pushing legislation to require tighter controls onsales of the fertilizer ammonium nitrate, which can be used to makebombs. Investigators isolated King and his staff in case they had beencontaminated, but allowed them to leave around 4:15 p.m. King, who had just come back from a legislative meeting onterrorism insurance, said the package was not opened by anyone onhis staff and he never touched the envelope.