Police in South Africa launched a manhunt after a mass shooting on Tuesday night that killed 12 people in an informal settlement in Johannesburg’s Cleveland suburb.

At least ten suspects, heavily armed with rifles, entered the Jumpers Informal Settlement in a white Toyota Quantum just before 11:00 p.m. local time and opened fire at multiple points before fleeing.

The police said the shooting left eight men, three women and an additional man who died in hospital from his injuries. Nine other residents were taken to hospitals with gunshot wounds.

The motive remains unclear. Police suspect the attack may be connected to a turf war among illegal mining groups that operate in the area, or it could stem from personal disputes or gang violence, all of which are common in informal settlements.

Provincial police Commissioner Lt Gen Tommy Mthombeni said Saturday that the area “is adjacent to an illegal mining zone” and that investigators could not rule out a link to illicit mining. The attack was described as “heartless” and “barbaric”.

South Africa’s informal mining activity has been growing amid its high murder rate – one of the world’s highest. Rifles and other firearms are widespread, with an estimated equivalent number of licensed and unlicensed guns circulating in the country.

Authorities are following all leads in an effort to locate the suspects, but no arrests have been made as of this writing.