Australia’s mergers arbitrator has reopened an investigation into mining giant Rio Tinto’s use of a deeply discounted rights issue to potentially take full control of former uranium miner Energy Resources of Australia, holder of the Jabiluka mineral lease in the Northern Territory.

Rio Tinto and aggrieved minority shareholders of ERA heard over the weekend that the Takeovers Panel would formally review an earlier decision to clear both ERA’s dilutive equity raising, and the ERA board and Rio Tinto’s conduct. It raises the prospect of a rare backflip from the highly esteemed regulatory body.