CHICAGO — Illinois prosecutors investigating alleged sexual abuse dating back to the 1980s against James Levine said Friday they won't pursue charges against the longtime Metropolitan Opera conductor, citing state law at the time, challenges in compiling evidence and other factors.

A statement from the Lake County state's attorney's office offers few details about the complaint lodged in 2016 with police in the Chicago suburb of Lake Forest, saying only that the alleged abuse occurred in the summers of 1986 and 1987 when the accuser was 16 and 17 years old.

"At the conclusion of the investigation, considering the specific conduct disclosed by the complainant, the age of the complainant at the time, all of the evidence in the case, and the applicable law ... it is our decision that no criminal charges can be brought," it said.

The one-page statement notes the statutory age of consent in Illinois at the time of the alleged abuse was 16, though the state has since raised it to 17 and to 18 in cases where the accused was in a position of trust or authority over the victim.

"We are bound to apply the law that was in effect at the time the allegations occurred rather than the law as it currently exists," the statement says.

The decision by prosecutors comes days after The New York Times published interviews with three men who said the 74-year-old Levine, among the most prominent classical music conductors in the world, had sexually abused them when they were teenagers. A fourth accuser later came forward.

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Levine, who the New York-based opera suspended following those reports, has denied the allegations.

"As understandably troubling as the accusations noted in recent press accounts are, they are unfounded," Levine said Thursday in a statement first published by the Times. "As anyone who truly knows me will attest, I have not lived my life as an oppressor or an aggressor."

The prosecutors' statement says none of the accuser's statements to investigators "included any allegations of force." And among the evidentiary challenges, it says, was that records from "the establishment" where the alleged abuse occurred no longer exist.

James Levine, then the music director of the Boston Symphony Orchestra, at its opening-night performance at Tanglewood in Lenox, Massachusetts, in July 2006. Michael Dwyer / AP

Levine's ties to the Chicago area go back decades.

He was music director for the Chicago Symphony Orchestra's summer residency at the Ravinia Festival from 1973 to 1993, and was to begin a term next summer as conductor laureate. The Ravinia Festival, north of Chicago, this week cut all ties with him amid the allegations.

Friday's statement doesn't name the Illinois accuser or provide other identifying details, such as the man's profession or hometown.

But the Times' reports included allegations from a man who said Levine sexually abused him in Illinois when he was 16. The paper reported a detective from the police department in the community of Lake Forest — which is near Ravinia in Highland Park — contacted the Metropolitan Opera last year about the allegations.

Details of the police report were first reported on the website of the New York Post. Levine's accuser, now in his mid-40s, contacted Lake Forest police in October of 2016 to report he'd had sexual contact with the conductor when he was under age 18.

The department assigned a detective who spent at least seven months investigating the allegations, according to a redacted copy of her written reports on the case. Earlier this week, prosecutors confirmed to The Associated Press the investigation was still active.

Related: Metropolitan Opera suspends conductor after sexual abuse claims

The accuser, who at the time was hoping for a career in music, told police the conductor had invited him to audition for him in New York and then encouraged him to engage in sexual "experimentation." He said his relationship with Levine extended well into adulthood and that the composer gave him money over the years when he was having financial problems.

In New York, the opera appointed Robert J. Cleary, a partner at the Proskauer Rose law firm, to investigate the accusations against Levine as it weighs his future.

In an earlier statement, the opera's general manager, Peter Gelb, said Levine wouldn't be involved in performances or other activities during the investigation.

"While we await the results of the investigation, based on these new news reports, the Met has made the decision to act now," Gelb said, adding that the opera's board and executive committee fully supported the suspension.

Gelb told NBC News on Sunday that the opera company first became aware of the allegations when Illinois police opened an investigation in October 2016.

Levine in response said it was his "fervent hope ... that in time people will come to understand the truth, and I will be able to continue my work with full concentration and inspiration."