(AP) — Mexico’s immigration service says a group of migrants threw rocks at its officers, injuring one severely. The National Immigration Institute said Tuesday the attack happened the previous day along railroad tracks in the central state of Tlaxcala. The institute says the officers approached a group of migrants walking along the tracks. The migrants reacted by throwing rocks. One officer was in serious condition at a local hospital with wounds to the face and skull. Attacks by migrants on immigration officers are very rare, though there have been scuffles and shoving matches in the past. The institute did not identify the migrants’ nationalities.