WASHINGTON – Al-Qaida terrorists have developed a crude device designed to spread deadly cyanide gas through the ventilation systems of crowded indoor facilities such as subways, according to a closely held security directive issued to law enforcement by the U.S. Department of Homeland Security and obtained exclusively by WorldNetDaily.

“Al-Qaida remains intent on using chemical or biological agents in attacks on the homeland,” says the internal warning. “Terrorists have designed a crude chemical dispersal device fabricated from commonly available materials, which is designed to asphyxiate its victims.”

Marked “For Official Use Only,” the five-page memo issued Friday says the device produces cyanogen chloride gas and hydrogen cyanide gas, and can be placed near air intakes or ventilation systems in crowded open spaces or enclosed spaces.

“These gases are most effective when released in confined spaces such as subways, buildings or other crowded indoor facilities,” adds the Homeland Security memo, which was distributed to federal agencies in anticipation of possible al-Qaida attacks around the end of the Muslim holiday Ramadan, which happens to coincide with Thanksgiving and the start of the regular holiday season.

Citing “recent information” from al-Qaida sources, the directive also warns of possible car-bombings in America, as first reported yesterday by WorldNetDaily, and advises security officials to take code-red protective measures to guard government buildings and gas and other chemical plants.

“Al-Qaida continues to plan attacks against U.S. targets,” the memo asserts.

Despite the high-threat measures, the administration has decided to keep the public terror-threat alert at yellow, or elevated. Phone calls to Homeland Security were not returned.

Experts in chemical weapons say al-Qaida is known to have sought a weapon to pump cyanide gas into ventilation systems.

“Al-Qaida has shown an interest in cyanide as a weapon,” said Amy Sands, former deputy director of nonproliferation studies at the Monterey Institute of International Studies in California.

She cites Ahmed Ressam, the terrorist convicted of plotting to bomb Los Angeles International Airport during the millennium celebrations. He claims to have been trained to kill people with cyanide at an al-Qaida camp in Afghanistan.

“His terrorist masters also taught him how to introduce cyanide gas into public ventilation systems in order to affect the maximum number of victims, while minimizing the risk to the perpetrator,” Sands said.

She also points to the nine al-Qaida-tied Moroccans arrested last year in Rome. They allegedly were planning to poison the water supply of the U.S. embassy with potassium ferrocyanide.

“Al-Qaida has shown a continued interest in targeting subways, rail systems, dams and water facilities” in America, the Homeland Security memo warns.

Noting the recent “sophisticated” car-bombings in Saudi Arabia and Turkey, it adds that the terror group may use “novel methods” to pull off such attacks in America, including disguising suicide bombers as women.

“Male bombers may dress as females in order to discourage scrutiny,” the federal memo warns.

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