Moroccan authorities say nine more people have been arrested in the slayings of two Scandinavian university students who were hiking in Morocco’s Atlas Mountains.

Morocco’s Central Bureau of Judicial Investigations says the latest arrests were made on Thursday and Friday across the country.

With four other men arrested earlier, that brings the total number of suspects in the case to 13. Moroccan investigators say those arrested were carrying arms and “suspicious materials” used in making explosives.

The bodies of the women from Norway and Denmark were found near the village of Imlil, a starting point for treks to Mount Toubkal, North Africa’s highest peak.

Authorities in Morocco consider the killings a terrorist act.

A plane carrying the caskets of the two slain European tourists, identified as 24-year-old Louisa Vesterager Jespersen and 28-year-old Maren Ueland, has taken off from Casablanca for Denmark.

The friends lived in southern Norway, where they attended university.

Norwegian criminal investigators are now trying to map the women’s activities before their departure for the village of Imlil.

The women’s bodies were found on Monday, sbout 10 kilometres from the village.

Morocco is generally considered safe for tourists but it has been routing out Islamic extremists for years.