Authorities in Las Vegas have issued a warrant to obtain the DNA of soccer superstar Cristiano Ronaldo to see if it matches that found on a dress of a woman who has accused him of rape, according to a law-enforcement official with knowledge of the case.

The authorities sent the warrant recently to the court system in Italy, where Mr. Ronaldo plays soccer, the official said.

Las Vegas police reopened the case in the fall after the woman, Kathryn Mayorga, filed a lawsuit alleging that Mr. Ronaldo raped her in 2009 in Las Vegas and then paid her $375,000 to keep it secret.

Mr. Ronaldo and his attorneys have repeatedly denied the rape allegations.

“Mr. Ronaldo has always maintained, as he does today, that what occurred in 2009 in Las Vegas was consensual in nature, so it is not surprising that DNA would be present, nor that the police would make this very standard request as part of their investigation,” Peter S. Christiansen, an attorney for Mr. Ronaldo, said Thursday.