STILLWATER, Minn. (AP) _ The husband of one of the state's most notorious murderers has died under suspicious circumstances, authorities said Friday. The woman was convicted in 1987 of beating their adoped son to death more than 20 years earlier.

Harold Jurgens, 78, of rural Stillwater died Thursday, and authorities had found evidence of unusual chemicals in his blood, Sheriff Jim Frank said. He said Lois Jurgens, 74, is not a suspect, and no one else is considered a suspect, either, but authorities do consider the death suspicious.

Mrs. Jurgens was convicted of third-degree murder in the 1965 death of the couple's 3-year-old adopted son, Dennis.

The investigation into the boy's death was reopened in the 1980s after Dennis' birth mother began searching for him and became suspicious when she learned that he was dead. The case drew widespread publicity and was the subject of a book and a made-for-television movie.

The sheriff said Jurgens had been in failing health for ``some time'' with heart trouble. On Wednesday, an unidentified tipster contacted authorities and expressed concern about Jurgens' welfare, suggesting he may have been poisoned, Frank said. An investigator met with Jurgens at a hospital before he died and, based on medical records and interviews, concluded there was evidence of unusual chemicals in his system.

But the sheriff was careful not to call the death a poisoning.

``We are just doing an investigation of a death, that's all,'' Frank said.

Mrs. Jurgens was released from prison in mid-1995 after serving eight years. Prosecutors contended Dennis died after numerous beatings and abuse, which including making the child eat food covered with horseradish and tying him spread-eagled in his crib.

Harold Jurgens had testified before the grand jury about the boy's death under a grant of immunity from the prosecution.