JOHANNESBURG (AP) — South African police say gunmen have opened fire on a minibus carrying members of a taxi drivers’ association, killing 11 people and critically wounding four others.

Police Brig. Jay Naicker says the victims of the Saturday night attack had attended a colleague’s funeral and were returning home when the ambush occurred. He says the attack happened between the towns of Colenso and Weenen in KwaZulu-Natal province and the victims were from Gauteng province.

Police are investigating possible motives.

Tensions between groups of taxi drivers vying for the same routes sometimes spill into deadly violence in South Africa.

South African media reported the deaths of 10 people in violence related to rivalries among minibus taxi drivers in Cape Town over one weekend in May.

[Feature image: Claudine Senegal/Ladysmith Herald via AP]