DHAKA—At least 15 people have been killed in a massive fire that ripped through a Rohingya refugee camp in Bangladesh, while at least 400 remain missing, the UN refugee agency said on Tuesday. “It is massive, it is devastating,” said UNHCR’s Johannes Van der Klaauw, who joined a Geneva briefing virtually from Dhaka, Bangladesh. “We still have 400 people unaccounted for, maybe somewhere in the rubble.” He said the UNHCR had reports of more than 550 people injured and about 45,000 displaced. Bangladeshi officials are investigating the cause of the blaze even as emergency and aid workers and families sift through the debris looking for further victims. The fire ripped through the Balukhali camp near the southeastern town of Cox’s Bazar late on Monday, burning through thousands of shanties as people scrambled to save their meager possessions. “Everything has gone. Thousands are without homes,” Aman Ullah, a Rohingya refugee from …