Prosecutors in Switzerland will not pursue a sex assault investigation into Roman Polanski, the film director who a German woman said had raped her as a teenager 45 years ago.

Renate Langer, a 61-year-old former actress, was the fourth woman to publicly accuse Mr. Polanski of sexual assault when she filed a police report with Swiss authorities in September. She said that the director had raped her when she was 15 at his home in the town of Gstaad. But prosecutors in Bern said on Wednesday that the statute of limitations has expired, according to a report in Reuters.

Herve Temime, Mr. Polanski’s lawyer, told the Associated Press that the allegations were “contested by Mr. Polanski and unfounded.”

Mr. Polanski, 84, is a fugitive from the United States. In 1978, he pleaded guilty to having sex with 13-year-old Samantha Geimer, but fled to France, which does not extradite its own citizens, before he was sentenced. In 2009, he was detained by Swiss police when he arrived in Zurich to attend the Zurich Film Festival and to accept a lifetime achievement award. The Swiss also declined to extradite him to the United States.