EMMA FARGE and ANGUS MCDOWALL A U.N.-appointed mission to Libya said there are "probable mass graves" yet to be investigated, possibly as many as 100, in a town where hundreds of bodies have already been found, and it urged Tripoli to keep searching. The report to be submitted to the U.N. Human Rights Council this week details how a militia run by seven brothers executed and imprisoned hundreds of people between 2016-2020, sometimes keeping them in tiny oven-like structures called "the boxes" which were set alight during interrogations. The evidence of kidnappings, murder and torture in Tarhouna, uncovered by the…