MINNEAPOLIS  — A man who authorities have called a person of interest in the 1989 abduction of a central Minnesota boy pleaded not guilty Monday to unrelated federal child pornography charges.

Danny Heinrich, 52, was indicted last year on 25 counts related to possessing and receiving child pornography. Authorities have said they found the images while investigating the disappearance of Jacob Wetterling, who was 11 when he was kidnapped.

While authorities call Heinrich a person of interest in Jacob’s unsolved abduction, he has not been charged in that case and has denied involvement.

Jacob was riding his bicycle with his brother and a friend on Oct. 22, 1989, when a masked gunman abducted him from a rural road near his home in St. Joseph. He hasn’t been seen since. Authorities decided to take a fresh look at the case last year.

According to court documents, Heinrich matched the general description of a man who assaulted several boys in nearby Paynesville from 1986 to 1988. In addition, Heinrich’s DNA was found on the sweatshirt of a 12-year-old boy who was kidnapped from Cold Spring and sexually assaulted nine months before Jacob’s abduction. Heinrich has not been charged in any of those cases, and the statute of limitations has expired.

Authorities searched Heinrich’s home in Annandale in July. According to the indictment, investigators found numerous three-ring binders around the home that contained suspected child pornography. Additional images were recovered from Heinrich’s computer.

Although Jacob’s kidnapping has generated more than 50,000 leads over the years, the crime remains unsolved and continues to haunt Minnesota law enforcement officers. It spurred new federal laws requiring states to create sex-offender registries. Jacob’s parents, Patty and Jerry Wetterling, founded the Jacob Wetterling Resource Center, which works to help communities and families prevent child exploitation, and Patty Wetterling became a national advocate for children.

During a hearing last year, Heinrich’s attorney noted that there were multiple suspects at the time of Jacob’s disappearance, and the assailant in many of the attacks outlined in court documents wore a mask.

Heinrich is scheduled to go on trial on the child pornography charges in July.