The deaths of two people from cyanide-laced Tylenol caps (AP) _ one in Tennessee, the other in New York - were caused by two different forms of the poison, Food and Drug Administration Commissioner Frank E. Young said today.

The FDA's laboratory in Cincinnati has identified the poison that killed Timothy R. Green, 32, in Nashville, as sodium cyanide, Young said in a statement issued in Washington.

''This is a different type of cyanide from the potassium cyanide found in the New York death of Diane Elsroth,'' Young said.

Tests also established ''the cyanide ... differs from any used in laboratories of the manufacturer of Tylenol,'' the New Brunswick, N.J.,-based Johnson & Johnson, Young said.

Green's body was found Sunday night in his home, two weeks after the Feb. 8 death of Miss Elsroth in Yonkers, N.Y., a New York City suburb.

''Nothing was found to indicate any connections between the two deaths,'' Young said.

The commissioner repeated his Feb. 14 warning that consumers should avoid taking all Tylenol capsules of any strength and any lot number.

In Washington, Young, an FBI official and David R. Clare, president of Johnson & Johnson, which manufactures Tylenol, told a Senate hearing today there is still no idea after an intensive investigation of who is responsible for the cyanide poisonings or how they happened.

They said, however, there was no evidence the tampering with the Tylenol capsules took place in the manufacturing process.

Clare said the New York poisoning appeared to be the work of ''a very sophisticated individual'' who penetrated the Tylenol capsules without leaving any visible traces.

Nicholas V. O'Hara, a section chief in the FBI's criminal investigative division, said the evidence of tampering was discovered only after a ''high- resolution miscroscopic examination.''

''We have not developed any suspects,'' O'Hara told the Senate Labor and Human Resources Committee. ''We don't anticipate this will be an easy investigation.''

Young and Clare said it was impossible to design an absolutely tamper-proof packaging, but Young said design improvements have made packaging of over-the- counter medicines such as Tylenol ''extremely safe'' for consumers.

Green's partially decomposed body was found on his bed over the weekend, and Metro Nashville medical examiner Charles Harlan on Wednesday ruled the Nashville guitar repairman had died from cyanide poisoning.

Harlan noted that an autopsy on Green's body uncovered no acetaminophen, the active ingredient in Tylenol. That led investigators to speculate that the victim either took a capsule that had been emptied of all the Tylenol ingredient and refilled with poison, or cyanide got into Green's body from some other source and the discovery of the Tylenol bottle was a coincidence.

Police were investigating whether Green's death should be classified as a suicide or homicide.

But close friends said Green, a devout Jehovah's Witness, would not have killed himself.

''I find it very hard to believe he would kill himself,'' said Peter Laves, his landlord and next-door neighbor. ''He loved to play the guitar and to play music that would make you laugh.''

''His whole life was wrapped around his door-to-door ministry,'' said Naomi Roberts, Green's girlfriend, who said she bought the bottle of Tylenol found beside Green's death bed at a neighborhood grocery, the Big Star Market.

The purchase of the Tylenol was still under investigation Thursday by local authorities, said Steve Watson, deputy director of the Tennessee Bureau of Investigation.

A Big Star spokesman said he had not been contacted by police and was unaware any possibly tainted Tylenol had been bought at the store.

''Every store in Nashville pulled Tylenol capsules off the shelves right after that whole stink started,'' said Wayne Ashworth, the market's assistant manager.

Johnson & Johnson pulled the non-aspirin pain-reliever in capsule form off store shelves Feb. 14, just days after Miss Elsroth died.

Her death occurred 3 1/2 years after seven people in Illinois died from ingesting cyanide contained in Extra-Strength Tylenol capsules.

The Tennessee Health Department issued its own ban on the capsules Wednesday, said Dr. Robert Hutcheson, the state epidemiologist.

Hutcheson warned people not to take the capsules, but he asked Tennesseans to save any Extra-Strength Tylenol in capsule form because the FDA and state officials want to collect samples.

In White Plains, N.Y., investigators of Ms. Elsroth's death said the possibility that cyanide was introduced into Tylenol capsules at the factory remains an active theory, despite the FBI's discovery of tampering in the packaging around the capsules.

''We don't consider this a major break and we'll still consider all alternatives,'' said Bruce Bendish, head of the Homicide Bureau of the Westchester County district attorney's office. ''We have eliminated nothing.''

The FBI said Wednesday that the packages containing the capsules that killed Diane Elsroth, 23, and another bottle of tainted capsules had apparently been tampered with ''independent of the manufacturing process.''