NEW YORK (Reuters) - Two Madonna fans ended their lawsuit in New York accusing the pop superstar of starting concerts two hours late, prompting her legal team to threaten the plaintiffs' lawyers with sanctions.

Michael Fellows and Jason Alvarez did not say in a Brooklyn federal court filing on Wednesday why they voluntarily dismissed their proposed class action against Madonna and tour promoter Live Nation with prejudice, meaning it cannot be brought again.

In a separate filing on Wednesday, the defendants' lawyer said the dismissal "was not the result of any settlement."

Fellows and Alvarez alleged false advertising and negligent misrepresentation after Madonna, 65, began three December concerts on her "Celebration Tour" at Brooklyn's Barclays Center after 10:30 p.m., though tickets promised an 8:30 p.m. start.

The plaintiffs said that because the concerts ended around 1 a.m. the next day, they had either to leave early or spend more to get home because of limited public transport and ride-sharing options, and see their plans for the next day disrupted.

Fellows and Alvarez, both of Brooklyn, said they would not have bought their tickets had they known about the late starts.

They said Taylor Swift and Bruce Springsteen, both promoted by Live Nation, start their concerts on time.

Jeff Warshafsky, the lawyer for Madonna and Live Nation, in a June 10 court hearing accused the plaintiffs of waging a harassment campaign aimed at "extorting" a big settlement.

In his filing on Wednesday, Warshafsky said the defendants viewed the case as a "frivolous strike suit designed to force them to incur legal expenses," and that they "reserve the right to move for sanctions, attorneys' fees, and costs."

Lawyers for Fellows and Alvarez did not immediately respond on Thursday to requests for comment.

A similar lawsuit by ticket purchasers against Madonna and Live Nation remains pending in the Washington, D.C., federal court over late-starting December concerts in that city's Capital One Arena.

The case is Fellows et al v. Ciccone et al, U.S. District Court, Eastern District of New York, 24-00357.

(Reporting by Jonathan Stempel in New York; Editing by Daniel Wallis)

By Jonathan Stempel