(CNN) Thirteen suspects have been arrested in connection with the beheading deaths of two tourists in Morocco, the state-controlled 2M news agency reported.

Four are suspected of killing 28-year-old Maren Ueland of Norway and 24-year-old Louisa Jespersen of Denmark. Of those four, one had previously served a two-year sentence in an extremism-related case, Boubker Sabik, a Moroccan national security spokesman, told 2M.

Nine others were arrested in different cities for their alleged connection to the four murder suspects, 2M reported.

During the raids, authorities found "suspicious substances that could potentially be used in making explosives," 2M said.

The bodies of Ueland and Jespersen were found Monday in the High Atlas mountain range.

Read More