(IDEX Online) - Petra Diamonds is facing claims that guards at its Williamson Mine, in Tanzania, switched rubber bullets for metal shot in their shotguns to inflict greater damage to trespassers.The UK-listed miner was accused last November of employing security staff who were responsible for seven deaths and 41 injuries in their "ruthless and militaristic" dealings with illegal diggers. It is currently investigating a series of claims made by UK corporate watchdog RAID.The latest allegations center on the type of ammunition used by contractors Zenith Security. RAID says it interviewed a former guard who explained how cartridges of rubber pellets were opened and deliberately re-packed with more dangerous metal pellets."Deliberately altering ammunition to cause indiscriminate injury, even death, to local residents raises serious questions about Petra Diamonds' oversight of security at its diamond mine in Tanzania, said Anneke Van Woudenberg, the organization's executive director, in a report published last week.Petra acknowledged RAID's report and said: "As previously stated, Petra takes the allegations of human rights abuses at the Williamson mine extremely seriously. "Petra has committed to provide feedback on the investigation being carried out by an external advisor, in conjunction with our legal advisors; the scope of this investigation already includes the allegations mentioned by RAID in their report. "As detailed in our recent announcements, the Company has taken a number of actions to address the situation at the Williamson Mine, including the replacement of the third party security contractor at the mine, as noted in our announcement on 9 February 2021."Pic courtesy RAID shows Zenith Security guards