Imminent Attack?

abclocal.go.com American law enforcement officials are warning that a terrorist attack could be imminent — with a focus on today and Friday — and on the nation's previous targets, Washington, D.C., and New York.

Hospital officials in New York have been warned to be prepared to deal with a possible cyanide attack, urging them to build up stocks of sodium thiosulfate, the antidote to cyanide poisoning, as well as treatments for biological and chemical warfare. Doctors were also warned to be on the lookout for clusters of patients with respiratory, neurological or skin conditions.

Meanwhile, police around the country have stepped up patrols and heightened security measures.

Black Hawk helicopters are patrolling the skies over the nation's capital, ready to call in F-16 fighter jets if planes try to violate restricted airspace, and on the ground the military has deployed heat-seeking Stinger missiles with a range of up to two miles, to be used if suspicious planes refuse to respond to orders to leave the area.

In New York, police are out in force in the subways, at train stations and airports and at the bridge and tunnel crossings into the city with radiation detectors and gas masks. Air patrols have also returned to New York.

The FBI and National Infrastructure Protection Center issued an alert to critical industries and key facilities that they should take steps to guard against potential terrorist attacks.

The bulletin advised checking for possible infiltrators among employees, varying security routines and checking Internet sites that describe their facilities to "consider how that information might assist terrorists interested in planning an attack. Operatives will likely research potential targets extensively prior to an attack."

The apparently increasing threat of new terrorism has Americans on edge. Hardware stores have had runs on flashlights and batteries, as well as on duct tape and sheet plastic, which the Department of Homeland Security has recommended for people to use to create secure rooms in the homes.

And it's not just in New York and Washington that people are worried.

"We have some extra food and water put back. An ounce of prevention can go a long way," said Jon McCormick of Indiana. "There is a grim mood from everyone about the possibility of attack, but everyone seems to be prepared to ride it out."

Threats Overseas, Too

American officials say the threat overseas may be just as great, particularly in the Arab countries cited in an audiotape from Osama bin Laden that aired on Arab television on Tuesday.

Among the prime targets, officials told ABCNEWS, could be Saudi Arabia's Ras Tanura oil refinery — the largest in the world. Police in London were putting on a show of force at Heathrow airport that rivals anything seen in the United States.

At Gatwick Airport, outside London, the North Terminal was closed today after police discovered a live grenade in the luggage of a passenger. The man, who police said was from Venezuela and was traveling from Alicante, Spain, was arrested and charged under the Prevention of Terrorism Act.

The State Department today issued travel warnings for Bahrain and Qatar, and upgraded the warning for Saudi Arabia that was issued on Jan. 30. The warnings authorize the voluntary departure of all non-emergency personnel and family members from the U.S. Embassies, and urge private American citizens to rigorously evaluate their own security situations.

‘Packages of Importance’

The heightened alert comes less than one week after the Department of Homeland Security announced that the nation's five-step alert system had been raised to "high," the first time the level had been increased since the anniversary of the Sept. 11, 2001, attacks.

Perhaps more significantly, though, it comes after U.S. intelligence intercepted suspected terrorist communications talking of "the underground" and "packages of importance."

The intercepted communication refers to the end of the hajj Muslim holiday, which is the end of this week and indicates plots with radioactive materials or chemical agents, law enforcement officials said.

"If given the choice, al Qaeda terrorists will choose attacks that achieve multiple objectives, striking prominent landmarks, inflicting mass casualties, causing economic disruption and rallying support through shows of strength," CIA Director George Tenet told the Senate Armed Services Committee.

While the preparations are being made to mitigate the effects of any possible attack, authorities hope that the show of force will rob terrorists of the element of surprise, and possibly forestall terrorists from following through on any plans.

New Bin Laden Tape?

Meanwhile, Washington officials are examining yet another audiotape that may be from bin Laden — the second tape from the al Qaeda leader to surface this week.

"He's obviously raising the confidence of his people. He's obviously exhorting them to do more," Tenet said of the first tape, which was aired on Arab television network al Jazeera on Tuesday. "What he's said is often followed by an attack."

A British-based Islamic news agency says it has a new bin Laden recording, in which the voice purported to be that of the terror mastermind predicts he will die "a martyr" this year in an attack against his enemies.

U.S. counterterrorism officials are reviewing a transcript of the tape, but so far they have not been able to confirm that it's an authentic message from the terror chief.

At the same time, the U.S. government is aggressively pursuing intelligence that Saddam Hussein may have sent operatives to the United States, ABCNEWS has learned.

Sources told ABCNEWS that the possibility of Iraqi infiltrators is one reason why the FBI has launched a massive campaign to interview 50,000 Iraqi-Americans and Iraqis living in the United States. Of particular interest are scores of Iraqis ordered by immigration judges to leave the country, but who may have disappeared.