An explosion tore through an apartment building in southern Ukraine, killing at least 13 people and leaving up to 24 trapped under the rubble, an emergency official said Thursday. The blast was caused by a suspected gas leak, leveled part of the five-floor building in the Crimea peninsula resort of Yevpatoriya and destroyed 35 apartments, said Emergency Situations Ministry spokesman Ihor Krol. Children were among the dead, he said. Russian television reported that those trapped under the rubble made calls to relatives on their cellphones pleading for a quick rescue after the blast on Wednesday evening. "There was a loud bang, and we rushed out and saw half of the building was missing," witness Sergei Yurchenko told Russian state television Channel One. "There were screams, and a child was crying." Krol said that 21 people had been rescued, four of whom were hospitalized.