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 U.N. 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 meagre possessions.

“Everything has gone. Thousands are without homes,” Aman Ullah, a Rohingya refugee from the Balukhali camp, told Reuters. “The fire was brought under control after six hours but some parts of the camp could be seen smoking all night long.”

Authorities in Bangladesh have so far confirmed 11 deaths.

Some 40,000 huts in the camp were burned down, said Mohammad Mohsin, secretary of the Ministry of Disaster Management and Relief, after visiting the camp.

Two major hospitals of the International Organization for Migration (IOM) and Turkish government were also destroyed, he told reporters in Cox’s Bazar.

“A seven-member committee has been formed to investigate the matter,” he said.

Sanjeev Kafley, the International Federation of Red Cross and Red Crescent Societies’s delegation head in Bangladesh, said more than 17,000 shelters had been destroyed and tens of thousands of people displaced.

More than a thousand Red Cross staff and volunteers worked with fire services to extinguish the blaze, spread over four sections of the camp containing roughly 124,000 people, he said. That represents around one-tenth of an estimated 1 million Rohingya refugees in the area, Kafley said.

“I have been in Cox’s Bazar for three-and-a-half years and have never seen such a fire,” he told Reuters. “These people have been displaced two times. For many, there is nothing left.”

BARBED WIRE

Some witnesses said that barbed wire fencing around the camp trapped many people, hurting some and leading international humanitarian agencies to call for its removal.

Humanitarian organization Refugees International, which estimated 50,000 people had been displaced, said the extent of the damage may not be known for some time.

“Many children are missing, and some were unable to flee because of barbed wire set up in the camps,” it said in a statement.

John Quinley of Fortify Rights, a rights organization working with Rohingya, said he had heard similar reports, adding the fences had hampered the distribution of humanitarian aid and vital services at the camps in the past.

“The government must remove the fences and protect refugees,” Quinley said. “There have now been a number of large fires in the camps including a large fire in January this year... The authorities must do a proper investigation into the cause of the fires.”

The vast majority of the people in the camps fled Myanmar in 2017 amid a military-led crackdown on the Rohingya that U.N. investigators said was executed with “genocidal intent”, charges Myanmar denies.