Nearly 40 people, including twelve children, are reported to have been killed in an explosion in a residential building in Syria's rebel-held city of Idlib.<br /> The Syrian Observatory for Human Rights said the building contained weapons and ammunition belonging to an arms trafficker. <br />Dozens of people remain missing and a search and rescue operation is underway.<br />The monitor said the previous death toll of twelve climbed after more bodies were retrieved from the rubble. <br />The cause of Sunday's explosion is not yet clear.<br />Idlib is Syria's last major rebel-held area and is expected to the next target for the government's military. <br />
