Investigators in the Tylenol poisoning probe are confounded by the contradictory tales of two bottles containing tainted capsules.

Authorities have been unable to find signs of tampering with the two packages and bottles whose capsules contained potassium cyanide. Because the packages came from different plants but contained chemically identical versions of potassium cyanide, officials say it does not appear possible that the containers could have been tampered with at the factory.

A poisoned capsule from one package purchased in Bronxville, N.Y., led to the death last weekend of a New York woman; the second package was taken from the shelf of a retail store two blocks from where the first package was purchased.

As in a "locked-room" mystery, once investigators cut open the triple-sealed packages, the poison was there, inside the red-and-transparent capsules.

The capsules themselves -- as opposed to the packages -- showed clear signs of tampering.

The printed word "Tylenol" on one end of a capsule and the marked dose "500 mg" on the other half, are carefully aligned when they come out of the factory. But the poisoned capsules were not in alignment. "It is utterly baffling," said James A. Murray, a spokesman for Tylenol maker Johnson & Johnson. "We just cannot understand what was done." He said it is almost as if the crime were committed because it was an "exquisite challenge" to break through the tough triple seals without leaving a visible mark.

After the seven tainted-Tylenol deaths in Chicago in 1982, the pharmaceutical industry spent $500 million to $1 billion to make tamper-resistant seals on over-the-counter packages.

They were made only partly to deter someone from getting into the packages, and mostly to make it easy for consumers to see whether the packages had been tampered with, according to Jack Walden, a senior vice president for the Proprietary Association, which represents most manufacturers of over-the-counter drug products.

But in the New York Extra-Strength Tylenol killing, the glued-down box top, the printed strip of plastic that is heat-shrunk into a tight seal around the neck and cap of the bottle, and the strongly glued, tough foil seal over the mouth of the bottle were bypassed.

Probably in the first bottle found, and definitely in the second bottle, the original factory seals on the box, neck and mouth were still in place when taken from the store shelves, according to a Johnson & Johnson spokesman. (Although the first bottle had been opened by the customer, police and Johnson & Johnson officials said the original packaging was recovered and it was determined that the seals had not been tampered with.)

Because of that, the possibility is raised that the poison might have been added to the capsules at the factory before the packages were sealed.

But the two bottles came from different lots -- one made in Dorado, Puerto Rico, and one made in Fort Washington, Pa. They were sealed at those factories and shipped to a warehouse in Montgomeryville, Pa., two months apart, one in May and one in July.

From this warehouse, the boxed and sealed packages are sent out in an apparently random fashion to many customers. Half a dozen to a dozen or more store chains in the eastern United States could be supplied from each packaged, numbered batch. Then, from the customers' warehouses -- in this case those of A&P food stores and Woolworth variety stores -- the lots are broken down and shipped to many different stores.

Food and Drug Administration (FDA) and other officials said that mathematically, it is extremely unlikely that the two bottles from different factories could wander through the many distribution paths in the eastern United States and arrive two blocks from each other in Bronxville. Going back to the tampering theory, then, speculation from FDA officials and experts in the packaging industry suggests that the next possibility is that someone did some elaborate and expensive tampering, involving special equipment to reseal or replace the heat-shrunk barriers.

So far, however, spokesmen for Johnson & Johnson said that indicators such as the lettering on the shrink-ring around the neck and the tautness of the foil seal over the mouth do not show signs of even that type of tampering.

Another possibility, also requiring heat-sealing equipment, would require cutting into the plastic bottle itself and somehow melting the cutout back into place after tampering with the capsules.

This episode, combined with the seven 1982 deaths in Chicago, has led Johnson & Johnson to reconsider whether it should be making Tylenol in capsule form. The Proprietary Association has scheduled an emergency meeting of company officials to take up that and other sealing questions.

The FDA and Johnson & Johnson emphasized that consumers can still safely purchase and use Tylenol in tablet and "caplet" form. The company has established a hotline: 800-237-9800.

Technicians at the FDA in Cincinnati analyzed the poison found in the two bottles. They were chemically identical versions of cyanide. They were found to be chemically different from the cyanide used in the 1982 Chicago killings and from the cyanide compound used as a cleansing agent for some equipment used in the manufacture of Tylenol. FDA spokesmen and Johnson & Johnson said they still think that the incident was a local one.