From his laboratory in France, Utah's cold-fusion pioneer B. Stanley Pons termed "interesting and encouraging" the high-energy announcements of stateside colleagues.

Scientists at private laboratories in Pennsylvania and Michigan on Thursday announced separate theories to explain the enigma that is cold fusion, saying Pons and his partner Martin Fleischmann overlooked crucial evidence.Pons hasn't seen details of the experiments questioning his conclusions but said he was encouraged that money is being invested in fusion research, although the larger amounts are in Europe, Japan and the Soviet Union.

Michigan physicists Frederick Mayer and John Reitz, at a news conference in Boston, said what has been termed cold fusion is actually a new kind of nuclear reaction, which may produce a new kind of particle, a "hydron."

Also Thursday afternoon, Randell Mills, president of Mills Technologies of Lancaster, Pa., discussed his theory, claiming an unknown reaction that produces heat and creates a new, smaller form of hydrogen. Mills' conclusion, if proven correct, would sweep away quantum physics theories that have guided scientists since the 1920s.

Both groups have had papers accepted in the scientific journal Fusion Technology. Both claim their conclusions are easy to duplicate, unlike those of Pons and Fleischmann.

Pons and Fleischmann, University of Utah chemists, announced in March 1989 that they had achieved fusion through experiments using palladium in heavy water. Their announcement was startling because it had been believed that enormous pressure and very high temperatures are needed to produce fusion, the reaction that powers the sun. Mastering fusion is one of the Holy Grails of science, believed the answer to solving the world's energy problem.

Haven Bergeson, a University of Utah physicist who also conducts experiments at the National Cold Fusion Institute, proclaimed Mayer's theory interesting.

"That's a kind of thinking that's useful to explore," Bergeson said, after reading an advance copy of Mayer's paper. "This is well-enough done that one has to look at it fairly seriously. In this business, you look for the least likely explanation."

But David Worledge, a physicist at Electric Power Research Institute, a utility consortium in Palo Alto, Calif., said while the new theories might be entertaining, they seem premature. Scientists are still struggling to produce results from cold-fusion experiments. When results are more consistent, theorizing will be appropriate.

Experiments continue inconsistently to generate heat or other byproducts thought to be evidence that fusion is occurring. "When you only get one result in a blue moon, it's impossible to be confident of what you have," Worledge said. "We're getting enough results to be provocative, not enough yet to be really scientific."