A 7-pound block of cyanide salt (searchwas discovered by U.S. troops in Baghdad at the end of January, officials confirmed to Fox News.

The potentially lethal compound was located in what was believed to be the safe house of Abu Musab Zarqawi (search), a poisons specialist described by some U.S. intelligence officials as having been a key link between deposed Iraqi leader Saddam Hussein and the Al Qaeda (searchterror network.

Cyanides salts are extremely toxic. According to the U.S. Department of Energy's Ames Laboratory, exposure to even a small amount through contact or inhalation can cause immediate death.

Zarqawi, believed to have been operating in Iraq before March's invasion, was still being sought by coalition forces. It was not clear if anyone had been apprehended in connection with last month's find.

Early last year, U.S. Secretary of State  Colin Powell (searchdetailed Zarqawi's significance in an appearance before the U.N. Security Council.

"Iraq today harbors a deadly terrorist network headed by Abu Musab Zarqawi, an associate and collaborator of Usama bin Laden and his Al Qaeda lieutenants," Powell said.

Zarqawi was described as a poisons expert with strong ties to the former Iraqi regime and the terrorist groups Al Qaeda and Ansar al-Islam. A Palestinian born in Jordan who fought in Afghanistan more than a decade ago, Zarqawi returned to Afghanistan in 2000 to oversee terrorist training camps, Powell told the Security Council.

"One of his specialties at the camp was poisons," Powell said. "When our coalition ousted the Taliban, the Zarqawi network helped establish another poison and explosives training center."

Zarqawi is believed to have begun establishing terror cells in and around Baghdad prior to the start of the war last March, and is thought by U.S. officials to still be in the country.

U.S. officials, who said they were getting new intelligence in the hunt for Zarqawi, also believe he had been attempting to produce large quantities of the toxin ricin in northern Iraq.

Fox News' Bret Baier and Ian McCaleb contributed to this report.