Police in London, Los Angeles and New York are working to untangle an ever-growing mass of sexual assault and harassment complaints against powerful men, creating challenges even for big cities used to handling celebrities.

Most of the cases stem from claims against media mogul Harvey Weinstein — but authorities say they've also taken complaints made against other men in power.

"It's an international phenomenon," NYPD Chief of Detectives Robert Boyce said when asked about investigations into Weinstein. "These ladies were sexually assaulted, harassed, and they acquired psychological damage, so we have to move very cautiously with anyone who comes in — and that's what we're doing."

High-powered attorneys make it harder

Unlike cases involving everyday people, pressure from the media and high-powered attorneys create added problems for investigators, and many of the recent allegations date back years, sometimes passing the statute of limitations.

Los Angeles police say they have 27 open investigations into entertainment figures, including actor Ed Westwick and agent Tyler Grasham, in addition to Weinstein.

The LAPD has also taken more than 30 other reports of sexual misconduct that occurred in other parts of the United States and overseas and referred those cases to other law enforcement agencies.

Sexual Harassment The Accused

Ed Westwick is accused of sexual assault. He denies the allegations. (Jordan Strauss/Associated Press)

Separately, Beverly Hills police say its department alone is investigating a dozen allegations of sexual assault involving figures in the entertainment industry.

London police say they are investigating sexual assault allegations from nine people.

In New York, detectives have received more than a dozen complaints from people who reported being abused by entertainment industry figures around the country, and they say most of those cases involve Weinstein. At least 75 have made allegations in the media against him that range from rape to inappropriate comments, but not all have gone to police.

Police have not said exactly how many active cases they have except for one, an allegation by actress Paz de la Huerta that Weinstein raped her in her New York City apartment in 2010. Boyce has said the agency had a credible case against Weinstein and was gathering evidence to refer to the Manhattan district attorney's office for possible charges.

Harvey Weinstein

Actress Paz de la Huerta is frustrated because prosecutors have not yet brought criminal charges against film producer Harvey Weinstein, after she accused him in October of raping her in 2010. (Omar Vega/Associated Press)

The methods by which the claims are investigated remain the same whether someone is famous or not — detectives are seeking business records, phone records, putting together timelines and tracking the movements of both people. Each case has to be separately investigated in each local jurisdiction and built from the ground up.

But the older the allegation, the more difficult the investigation.

Plus, police may believe they have enough evidence to arrest someone, but it's up to the local district attorney offices to decide whether to prosecute.

Paz de la Huerta 'threw down the gauntlet'

In New York, Manhattan prosecutors haven't yet decided whether to proceed with de la Huerta's claims after she called the hotline on Oct. 25 to report the assaults. The delay has prompted the actress's attorney to publicly put the pressure on.

"We threw down the gauntlet on behalf of our client," attorney Carrie Goldberg said in a statement, "and urged DA NY to convene a grand jury by the end of next week (the week of Dec. 3) or expect the protests to begin."

Weinstein's lawyers have said he denies any nonconsensual contact. He has not been arrested and his whereabouts are unknown, though his company was headquartered in New York.

L.A. police detectives have already closed some of the investigations related to entertainment figures that were launched in recent weeks, including a case involving actor Corey Feldman, who said he was sexually abused as a child actor in the 1990s. Investigators said the case was closed after detectives determined the statute of limitations had expired.

Sexual Harassment The Latest

In this 2013 file photo, Corey Feldman performs in Los Angeles. The Los Angeles Police Department said it is no longer investigating sexual assault claims filed by the actor Feldman because the statute of limitations has expired on the case. (Katy Winn/Associated Press)

The open criminal investigations in Los Angeles include an allegation by an Italian actress and model who said she was raped by Weinstein in 2013 and allegations that Weinstein committed lewd acts in 2015. Los Angeles police Chief Charlie Beck has said investigators are working closely with New York City detectives.

Los Angeles prosecutors launched a task force this month to evaluate cases that are referred by police for criminal prosecution. But so far no cases have been referred to the district attorney's office.

The alleged offences occurred between the early 1980s and 2015. All involve the same alleged attacker, whom the police have not identified, but was widely reported to be Weinstein.

British police usually do not name suspects until they have been charged.