AFGEM, the South African-based tanzanite mining company, claims it has been attacked underground at its mine in Tanzania, according to an African newswire report. Quoting an AFGEM press release, the report noted that AFGEM alleged the “invasion” was well planned and financed by owners of small-scale mines in Block B, who it says are tunneling into AFGEM’s Block C lease and illegally mining.

AFGEM reportedly counted approximately 100 attackers—using weapons that included guns, knives, homemade grenades, and petrol bombs—storming Block C from below. According to the newswire, nine people were injured and several were arrested by police.

While the cause of the purported fighting hasn’t been confirmed, it’s been reported that, for the past two years, AFGEM’s Block C lease has been trespassed from both above and below the surface. AFGEM blamed mining officials and Arusha police for not defusing the tension between AFGEM and small-scale miners.

AFGEM’s claims have not yet been verified.