WASHINGTON (AP) _ The arrest itself took only moments. Now comes the painstaking, unglamorous laboratory work to determine _ with certainty _ whether the truckloads of evidence taken from Theodore Kaczynski's remote Montana cabin link him to the 17-year string of Unabomber attacks. And that work likely will take weeks.

Federal law enforcement officials had a lot of evidence even before agents started combing Kaczynski's cabin last week. Aside from some letters and the Unabomber's 35,000-word manifesto published by The Washington Post and The New York Times, that evidence consisted mainly of the remains of 15 bombs that killed three people and injured 23. One of the Unabomber's explosives was defused.

``What they're looking for are things which are consistent with those remnants,'' said John Hicks, who headed the FBI's crime lab for five years until his retirement in 1994.

Kaczynski has been charged only with possession of bomb parts and not with any of the Unabomber attacks.

``There has been an extraordinary amount of work done over the last 17 years to analyze and look at the evidence from the crime scenes, the communications from the Unabomber and the physical evidence,'' said Milton Ahlerich, who succeeded Hicks until his own retirement in January.

That includes such things as fingerprints and tool marks, biological examinations of such things as hair, fibers and DNA and chemical analysis of explosive residue to determine the exact composition of the bombs.

And the quirks of the typewriter used to type the manifesto and other missives. All were typed on the same typewriter, according to a senior federal official in Washington, who said investigators believed he had done so deliberately to give them a way to authenticate them.

U.S. News & World Report says in its April 22 edition that FBI crime lab experts have determined that the third typewriter removed from Kaczynski's cabin is the machine on which the manifesto and other letters were typed. In addition, law enforcement sources said FBI agents at the cabin discovered what they say is the original copy of the manifesto manuscript near that third typewriter.

Federal officials said the manuscript left little room for doubt that Kaczynski was the Unabomber, The New York Times reported Saturday.

Agents from the FBI, the Bureau of Alcohol, Tobacco and Firearms and the Postal Inspection Service have been carefully inspecting and then removing truckloads of evidence from the 10-foot-by-12-foot cabin, including one live bomb, one partly built explosive and parts of the cabin itself, sources said. The evidence is all being shipped back to the FBI lab in Quantico, Va.

But the agents are not simply crating up everything in sight. A federal judge this week sealed the cabin and surrounding property for 30 days so agents can conduct repeated searches.

FBI Agent Terry Turchie said in an affidavit that in bombing investigations, ``it is common to conduct multiple searches of the same premises to search for and secure evidence, the significance of which was not fully known at the time of the initial or previous search.''

Armed with analyses of bomb parts, some of which can take two weeks or more, agents can look for evidence not previously sought, said Turchie, assistant special agent in charge of the San Francisco office's Unabom division.

One might think it shouldn't take weeks to examine such a small cabin. But when explosives are involved, any object might be a bomb ready to blow or a booby-trap.

``Despite what you see in the movies, where they call in the bomb squad and some guy goes in and cuts the wire as the music reaches a crescendo, you just don't do that,'' Hicks said.

The first order of business is to make any unknown object safe. So agents brought in X-ray equipment to scan the cabin's contents. Also useful are robots that can take X-rays or move boxes away from agents.

Another technique is to ``put a string around it _ a long string _ and give it a yank from a distance,'' Hicks said. ``If it doesn't go off, then maybe you take the next step.''

Once the explosives are gone, agents must decide what might be evidence.

Something like copper wire might seem ubiquitous, impossible to identify as belonging to one person. However, chemical testing could reveal contaminants making it unique, such as elevated levels of lead or barium, he said. The plastic insulation also might reveal unique properties.

Wire cutters found at the cabin could provide more clues.

``Anytime you have any kind of mechanical action between a piece of metal and a tool, the tool can transfer marks from its cutting edge,'' he said. ``If the tool has been sharpened, it might have grinding marks that produce fine scratches. Those imperfections in the tool would be transferred to anything it came in contact with.''

Despite the power of the Unabomber's explosives to maim and kill, such things as insulated wires have survived and are available for comparison with the tools and other evidence found in the cabin, he said.

To see if others were in Kaczynski's cabin, agents might check for fingerprints, probably using something like a roach bomb that emits a vaporous superglue that sticks to fingerprints, Ahlerich said.

Hicks sounded somewhat wistful when asked if he wished he were back at the bureau right now.

``This stuff is exciting,'' he said. ``This is what it's all about. All these years, the frustration that developed. ... There is a sort of feeling like gee, I wish I could be there.''