Twin explosions in China's northern port city of Tianjin were so powerful that people for miles wondered whether they had been nuked.
So ground-shaking that the blasts registered as an earthquake.
So huge that the fireballs could be seen from space
At least 50 are dead and 700 injured - and 18 firefighters are still missing, down from three dozen, NBC reports.
The two blasts happened in a warehouse packed with hazardous chemicals, the BBC said.
State-run Xinhua reported only that the warehouse housed “dangerous goods".
"The volatility of the goods means the fire is especially unpredictable and dangerous to approach," Xinhua said.
Tianjin city officials had called a meeting with area companies one week earlier over concerns about safety standards. The Tianjin Administration of Work Safety posted a notice about the meeting on its website, Reuters reports.
China's President Xi Jinping said a full probe with "transparent information disclosure to the public" is underway and vowed those responsible will be "severely handled.”
For now, he said in state media, authorities must "make full effort to rescue and treat the injured and ensure the safety of people and their property.”
More than 1,000 firefighters responded.
The Wednesday night explosions were picked up by space satellites in space quake detectord monitored by the U.S. Geological Survey.
The port is the 10th largest in the world and the images are stunning: crumpled shipping containers were thrown around like match sticks, hundreds of new cars were torched and port buildings left as burnt-out shells, witnesses told Reuters.
"I was sleeping when our windows and doors suddenly shook as we heard explosions outside. I first thought it was an earthquake," Guan Xiang, who lives four miles away, told Reuters by telephone.
Guan, 24, said he saw a mushroom cloud in the sky.
The White House has expressed its condolences to China.
Xinhua has reported that a fire broke out in several massive shipping container before the biggest blasts.
China's safety standards are considered sub-par in the country's booming economy compared to the West and industrial accidents on this scale have happened before.
A car parts factory explosion a year ago killed 75 people.