The 400 to 500-page document, mainly in Spanish, must first be translated "then the prosecutors will decide on the continuation of the preliminary investigation," the prosecutor's statement said.
The translation will take several weeks, a spokesman for the prosecutor told AFP.
The 45-year-old Assange was questioned in London over two days ending November 15.
Swedish prosecutor Ingrid Isgren, Ecuador's ambassador to Britain, Carlos Ortiz, and an Ecuadorian lawyer representing Assange were all present as the former computer hacker was grilled on questions provided by Swedish officials.
The Australian had sought refuge in Ecuador's embassy in London's upmarket Knightsbridge neighbourhood in June 2012, fleeing allegations of rape and sexual assault in Sweden dating back to 2010.
Assange has denied the claims calling them politically motivated.
He has refused to travel to Sweden for questioning, saying he feared he would then be extradited to the United States where he is wanted over WikiLeaks' release of 500,000 secret military files on the wars in Afghanistan and Iraq.