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Chicago’s Patrick Kane on Tuesday. He is accused of rape but has not been charged.Credit David Banks/Associated Press

BUFFALO — A lawyer for the woman who has accused the Chicago Blackhawks star Patrick Kane of rape announced at a news conference Wednesday that a rape-kit evidence bag was left on the doorstep of the accuser’s mother Tuesday afternoon. But police officials quickly dismissed the claim as untrue, even as it raised new questions about the investigation in the increasingly bizarre case.

The rape kit was not inside the brown paper evidence bag when it was found, said the lawyer, Thomas Eoannou, but the bag contained identifying information, including his client’s name and birth date and the name of the hospital where the rape kit was collected, Erie County Medical Center.

Eoannou brought the bag to a news conference he had called at his law office and said it had been authenticated, although investigators disputed that contention hours later.

“All evidence related to this case that was given to Erie County Central Police Services by the Town of Hamburg Police Department is accounted for and remains in its original packaging in the possession of Erie County Central Police Services,” the Central Police Services commissioner, John Glascott, said in a statement released Wednesday afternoon. “This includes the evidence in the rape kit and the packaging itself.”

The back and forth was the latest twist in the case involving Kane, a three-time Stanley Cup winner and one of the best players in the N.H.L., and his unnamed accuser. She told the police that Kane had raped her in his $2.6 million lakeshore home near Buffalo in the early hours of Aug. 2, after they had met at a nightclub.

She was examined at a hospital and was found to have scratches on her legs and bite marks on her shoulder, The Buffalo News reported.

Kane has not been charged in the case, and he told reporters last week that he had “done nothing wrong” and that he expected to be exonerated.

At Wednesday’s news conference, Eoannou, the woman’s lawyer, passed around photos of the package, with the identifying information redacted, and said that the accuser’s mother found it when she returned home at about 1:30 p.m. Tuesday.

If it is authentic, the envelope’s existence outside the chain of custody will seriously taint the investigation of Kane, a 26-year-old All-Star.

“We’re hoping to find out how this happened and who had the incentive to modify and tamper with the evidence,” Eoannou said, “and finally get to the bottom of it, rather than have misinformation about semen and undergarments.”

Eoannou was referring to leaked news reports that had suggested that Kane’s DNA evidence was not detected in the rape kit, which is used by medical personnel to gather physical evidence.

The consequence of the leaks, Eoannou said, has been to discredit his client.

Kane’s lawyer, Paul Cambria, played down Eoannou’s disclosure in comments to The Chicago Tribune, saying that the results of the rape kit had been released to both sides in the case two weeks ago and that they had not implicated Kane.

“The evidence technician who works for the county tested it,” Cambria told The Tribune. “He said there was no Patrick Kane, and that’s all I needed to know.”

Eoannou said that his client disputed the leaks about DNA evidence and that she intended to pursue prosecution.

“This is a significant development in this case,” Eoannou said. “We need to bring in the F.B.I. or state troopers or some other law enforcement agency to try and figure out who had that bag, who put it in my clients’s mother’s doorstep, and why.”

The police in Hamburg, a suburb 20 miles south of Buffalo, acknowledged in early August that Kane was the subject of an investigation involving forensic testing for an episode that the accuser said took place at his summer house on Aug. 2.

Under increasing scrutiny, Kane kept a low profile, canceling appearances with the Stanley Cup in Buffalo, his hometown, where he had celebrated publicly in the past.

Kane has been in trouble during the off-season before. In 2009, he and his cousin James Kane were arrested in Buffalo and accused of punching a cabdriver in a dispute over a fare. The two pleaded guilty to disorderly conduct and were given conditional discharges.

Kane’s carousing has courted attention, too. Months after his run-in with the Buffalo cabdriver, he and his Chicago teammates Kris Versteeg and John Madden were photographed shirtless in the back of a limousine in Vancouver with a group of women. Kane apologized for that incident, and again in 2012 for photos that showed him appearing intoxicated at Cinco de Mayo celebrations at the University of Wisconsin soon after Chicago was eliminated from the playoffs.