The messages in anthrax-contaminated letters read "Death to America" and "Death to Israel." The work of a foreign terrorist, or a homegrown attacker manipulating his countrymen like the Wizard of Oz?

Arguments can be made for either case, whether you analyze the content of the letters or try to tie the anthrax to a particular country.

"Everything you look at is like a mouse trail," said Clint Van Zandt, a retired FBI agent and profiler. "You think you're going somewhere and it splits into two or three or four trails."

Bush administration officials said they have been unable to connect the Sept. 11 airline hijackings to the letters, which used the same date but were postmarked later.

The letter sent to NBC News anchor Tom Brokaw appears to be a copy of one sent to the New York Post. The third went to Senate Majority Leader Tom Daschle. The letters use short sentences with block printing, as if they were written by a youngster.

Homeland Security Director Tom Ridge said Thursday the anthrax contained in the Daschle letter had been altered to make it more of a threat.

He identified the strain of anthrax in all three letters as Ames, a substance named for the university city in Iowa, and used in American bioweapons research and in vaccine testing.

Besides the United States, there are nine countries known to have pursued anthrax weapons, including some of the hostile nations that U.S. authorities have worried about for years. They are North Korea, Iraq, Iran, Russia, China, Libya, Syria, Israel and Egypt.

When analyzing the content of the letters, the trail forks again.

Is the grade-schoolish block lettering the work of a foreigner who can't write English script?

Does the misspelling of penicillin ("penacilin" in the letters) indicate a foreigner without a dictionary?

Are the foreign-oriented messages about America and Israel what they seem to be on their face, or a diversion?

Or ...

Was it an American who would use the U.S. style for a date: "09-11-01"?

Is an American more likely to spell penicillin the way it sounds rather than look it up?

Since Americans have known homegrown terrorism in the past decade, could this be another Timothy McVeigh or Unabomber Theodore Kaczynski — criminals with a misguided cause?

"I think it's someone who's playing with us," said former CIA counterterrorism chief Vincent Cannistraro. "I think it's a nut. I don't think it has anything to do with foreign stuff."

Van Zandt said the misspelling of penicillin could be the work of a foreign national or an American with poor spelling skills.

He noted the number "1" is written with a short diagonal line at top and a line at the bottom, something many Americans do.

The use of a school for a return address could indicate the writer was an American who would know such a letter likely would be delivered to a member of Congress. The return address on the Daschle letter was "4th Grade, Greendale School, Franklin Park, NJ 08852." Officials said no such school exists.

Van Zandt, who in the Unabomber case was able to match Kaczynski's letters to his manifesto against technology, said the anthrax attacker could be an American trying to send a message — perhaps one who believes the nation needs a wakeup call to prepare for a bioterrorism attack.

He said speculation on a foreign-based terrorist could focus on the Sept. 11 date in the letters, the day of the airline hijacking attacks.

The hijackers could have given the letters to supporters or fellow plotters as the second phase of their attack, Van Zandt said.

He said it's possible that a foreign-based group unrelated to the hijackers "had this capability on the shelf but hadn't had the right opportunity to do it." Such a group might have figured that everyone would blame the hijackers, he said.

Cannistraro said he believes an American would be more likely to misspell penicillin because a foreigner masquerading as an American would have been using a dictionary. "He wouldn't have pulled it out of the air like an American," he said.

He added, "This is some American trying to imitate a foreign terrorist group. It's deceptive. There are no demands in the letters, only an attempt to inspire fear, create paranoia and impress the recipients with how powerful they are."