Swedish chief prosecutor Ingrid Isgren arrived at Ecuador's embassy in London Monday where she and another Swedish official will witness questioning of WikiLeaks founder Julian Assange, set to be interviewed later in the day by Ecuadorean prosecutor Wilson Toainga.

The interview was announced last week by the Swedish prosecution office and could end a long diplomatic deadlock that has seen the WikiLeaks founder holed up in the London residence since 2012.

Swedish authorities want to question Assange over allegations that he committed rape in 2010. Assange denies the allegations. “A DNA sample will also be taken, provided that Julian Assange agrees to it,” the prosecutor’s office said.

Last week Assange welcomed the news through his lawyer, saying he was looking forward to the “chance to clear his name.”

On Monday, supporters outside the Ecuador's London embassy held signs with message such as "Free Assange" and "U.S.A., hands off Assange." The WikiLeaks founder fears extradition to the United States, where he could face charges such as espionage for releases thousands of secret documents to the public.

After the interview, the Swedish officials will deliver a report on the interview to the Swedish prosecutor who will then evaluate whether the investigation should continue or not.

If Sweden eventually drops the investigation and Assange leaves the embassy he could then be arrested by British authorities for breaching his initial bail conditions.

The whistleblower jumped bailed and took refuge at the Ecuadorean embassy in 2012 days before he was to be extradited to Sweden because he feared that he would then be handed over to U.S. authorities.

In February, a U.N. panel said his stay at the Ecuadorian embassy equaled arbitrary detention, that he should be allowed to leave and be awarded compensation.

The Australian national claims he refused to travel to Sweden for questioning because he feared extradition to the U.S. over WikiLeaks’ release of 500,000 secret military files on the wars in Afghanistan and Iraq.

Swedish prosecutors dropped a sexual assault investigation, concerning another woman, against Assange in 2015 after the five-year statute of limitations expired.

But they still want to question him about the 2010 rape allegation, which carries a 10-year statute of limitations. Assange insists the sexual encounters in question were consensual.

Last month, the Swedish prosecutor’s office rejected Assange’s request to temporarily suspend his arrest warrant so he could leave the Ecuadorean embassy to attend the funeral of his mentor, Gavin MacFayden.

Making sure Assange did not escape from the Ecuadorian embassy has been an operation that has cost the U.K. police over US$18 million.