MUMBAI: The police detained 18 members of Save Aarey group after they protested against axing of trees on a plot where Mumbai Metro Rail Corp Ltd (MMRCL) plans a car depot for Colaba-Bamdra-Seepz line.Environmentalists had received a setback after National Green Tribunal refused to entertain their plea on declaring Aarey a forest.Yash Marwah of the group said, "We were protesting as MMRCL or its contractor had been cutting trees in the absence of a tree officer. They produced permission to cut trees, but as per rules, cutting can only be done in the presence of a tree officer."Activists had begun gathering from morning and there were around 80 protesters by afternoon. Marwah said, "MMRCL was asking police to press charges against us for obstructing work. Around 18 of us were detained and told to give it in writing that the work will not be obstructed in future." Around 3,000 trees are likely to be affected due to depot work.An MMRCL spokesperson said, "The Tree Authority has approved cutting of trees essential for ramp, pylon shifting and other Metro-related activities in three proposals. The tree-cutting carried out is strictly as per approval by the Tree Authority. MMRCL always conducts its activities by following legal procedures."MMRCL said the depot will be built on 25,000 sq m of land, even though it has 30,000 sq m in its possession.