Nineteen people have been arrested in the wake of the murder of two Scandinavian women last week in Morocco’s Atlas Mountains, a security source familiar with the case said on Monday.

They include the four main suspects in the crime and fifteen other people accused of having connections to the alleged killers, the source told Reuters, without giving further details.

Louisa Vesterager Jespersen, 24, from Denmark, and Maren Ueland, 28, from Norway were found dead early on Dec. 17 near the village of Imlil on route to Toubkal, North Africa’s highest peak and a popular hiking and trekking destination.

The four main suspects, aged between 25 and 30 years, had pledged allegiance to Islamic State in a video made three days before the bodies were found, but without agreeing this in advance with any foreign group, police and domestic intelligence spokesman Boubker Sabik said on the state 2M TV channel on Sunday.

Electronic devices, an unauthorized hunting rifle, knives and materials that could be used for bomb-making were found during police raids.

Compared with other countries in North Africa, Morocco has been largely insulated from militant attacks. The most recent took place in April 2011, when 17 people were killed in the bombing of a restaurant in Marrakech. In 2017 and 2018, Morocco dismantled 20 militant cells planning attacks in the country.