Rare Earth Minerals (REM) announced it has upped its stake in the Sonora Lithium project in Mexico to 11.85% through further on-market purchasing which now totals around £0.2m.The exploration group has increased its stake from the previously reported 11.27%. This interest, when combined with REM's 30% direct interest in the Fleur- El Sauz Lithium Joint venture, results in a total economic interest of around 38.29%.As of 10:54 the share price had risen 0.46% to 1.08p.WS