A.J. Simmonds, a prominent Utah historian who unwittingly became involved with document forger and bomber Mark Hofmann, died Sunday in an apparent cyanide poisoning and an explosion at his home.

Investigators are considering the case a suicide.A preliminary report from the state Medical Examiner's office revealed traces of cyanide in Simmonds' system. A bottle of the substance was recovered from the house, said Cache County Sheriff's Lt. Lynn Nelson said.

The cause of the explosion remains under investigation. However, fire investigators found a fitting had been removed from a natural gas line located next to the house's furnace, Nelson said.

Simmonds, 52, who had served as curator of archives and special collections at Utah State University's Merrill Library for the past 28 years, was found buried beneath debris near the front of the house shortly after the 9 a.m. explosion. His wife and two sons were not home at the time.

Investigators from the Cache County sheriff's office, state fire marshal's office, the FBI, the Bureau of Alcohol, Tobacco and Firearms and the gas company were dispatched to the scene.

The explosion was felt throughout the small rural community of Trenton, which is located north of Logan near the Utah-Idaho border. Cache County Sheriff Sid Groll said dispatchers received a number of calls reporting the blast at 9:09 a.m.

Firefighters from Trenton and Lewiston responded and found two-thirds of the two-story frame house had collapsed. Some minor fires were quickly ex-tin-guished.

Renowned for his expertise in Utah and Mormon history, Simmonds was also an adjunct professor at USU and a regular columnist for the Logan Herald Journal."This is a tremendous loss to the university and to the community," said Paul M. Norton, vice president for university relations at USU. "We've lost an individual who had knowledge and information that isn't duplicated anywhere." Norton said Simmonds was a prolific writer who was able to capture the spirit of a historic era as well as modern-day Cache Valley.

"He was one of our stars, one of our diamonds," Norton said. "It's all such a shock; it doesn't seem real."

Simmonds was a native of Trenton and grew up in the house that was destroyed on Sunday, according to Max Peterson, director of library and information services and Simmonds' direct supervisor.

Peterson said Simmonds was hired as curator of archives and special collections after he obtained his master's degree from USU. Over the years, Simmonds expanded the history archives from about 30 shelf feet of materials to more than 75,000 items, including hundreds of thousands of photographs.

Although the archives focus mainly on Utah and Mormon history, Simmonds was also credited with acquiring a world-renowned Jack London collection.

"His loss is a tremendous loss of research skills and understanding of topics of importance to our region and state," Peterson said. "He was a genealogist with few peers and was noted for his willingness to allow scholars to use our special collections."

Simmonds was also one of the founders of the Conference of Intermountain Archivists, a professional association of leading historians throughout the West.

That Simmonds killed himself 10 years after the Mark Hofmann case broke was not lost on some people who were close to the Hofmann case.

In 1985, Hofmann placed two bombs, killing Steven Christensen and Kathleen Sheets and then accidentally exploded one in his own sports car. He is serving a life prison sentence for the murders, which he committed to keep people from exposing him as a forger of historical Mormon documents.

"The (Simmonds blast) is interesting," said Allen D. Roberts, who co-authored Salamander, a book on the Hofmann story. "It's tempting to put that together with the Hofmann thing. But I'd look at the rest of his personal life and see what's going on." Simmonds had recently separated from his wife.

Despite Simmonds' expertise as a historian, he was among the first of many people duped by Hofmann. Simmonds, in fact, wrote a lengthy article in the magazine BYU Studies in 1980 expounding on the Anthon transcript, which later turned out to be a forgery.

Dick Forbes, an investigator with the Salt Lake County attorney's office, said Simmonds was the first person to whom Hofmann ever sold a forged document.

"A.J. said he was obviously taken in and felt foolish for putting so much trust in Mark," Forbes said.

According to Roberts, Sim-monds was Hofmann's mentor in historical documents and unwittingly became an important source of information for Hofmann's forgery career.

"I think they became friends, and Hofmann pretty much had the run of the place as Simmonds' assistant. Simmonds made it possible for Hofmann to get connected to some of the other archives . . . Hofmann used the system to his advantage."

Roberts said Simmonds' suicide is intriguing because the man was "complex and probably had lots of demons."

"It's ironic he would do this in his ancestral home because of his sense of history."

Simmonds is survived by his wife, Jeannie F. Simmonds, and his two sons.

Deseret News staff writer Nicole Bonham contributed to this report.