The woman who is in her 30s was arrested in Spain on February 13 and has previously been arrested in her absence. This weekend she was arrested in Sweden after being extradited.
Earlier, two men are arrested on probable cause for the murders in Piteå.
One of the men was arrested shortly after the suspected double murder – which according to the arrest request was committed sometime between 29 and 31 January. The other man was arrested in February, according to information to Aftonbladet at Arlanda Airport.
The two dead men, in their 60s and 65 years, were found dead in a villa in Piteå on Friday evening on January 31.