Beirut’s explosion started with a smaller blast followed by a much larger one.
Two explosions shook Beirut, the second one with enough force to break windows over a radius of miles, damaging and shaking buildings, and strewing debris over a wide area.
Videos posted online showed a shock wave erupting from the second explosion, knocking people down and enveloping much of the center city in a cloud of dust and smoke. Cars were overturned and streets were blocked by debris, forcing many injured people to walk to hospitals.
Flames continued to rise from the rubble well after the explosions, and a cloud of smoke, tinted pink in the sunset, rose thousands of feet into the sky.
One blast may have come from a fire at a fireworks warehouse, state-run media said.
At least one explosion, at about 6 p.m., stemmed from a fire at a warehouse at Beirut’s port, according to Lebanon’s National News Agency.
There were local reports that the warehouse contained fireworks, and in several videos posted online, colored flashes could be seen in the dark smoke rising from the fire, just before the second explosion.
But it was not clear if fireworks alone could have or did cause the massive blast.
The governor of Beirut, Marwan Abboud, speaking on television, could not say what had caused the explosion. Breaking into tears, he called it a national catastrophe.
Major General Abbas Ibrahim, the head of Lebanon’s general security service, toured the damage and said, “it is not possible to get ahead of the investigations and say that there was a terrorist act,” the National News Agency reported.
The toll of the explosion was not clear, but videos of the aftermath posted online showed wounded people bleeding amid the dust and debris, and places where flying debris had punched holes in walls and furniture.
The Lebanese Red Cross said that every available ambulance from North Lebanon, Bekaa and South Lebanon was being dispatched to Beirut to help patients.
Prime Minister Hassan Diab announced that Wednesday would be a national day of mourning, the National News Agency reported. The Lebanese presidency said on Twitter that President Michel Aoun had instructed the military to aid in the response, and called an emergency meeting of the Supreme Defense Council on Tuesday evening.
The explosions hit Beirut’s northern, industrial waterfront, little more than a mile away from the Grand Serail palace, where Lebanon’s prime minister is based. Many landmarks, including hospitals, mosques, churches and universities are nearby.
They erupted next to a tall building called Beirut Port Silos, at or near a structure identified on maps as a warehouse. Videos showed only twisted metal and chunks of concrete where that warehouse had been, some of it identifiable as the remains of trucks and shipping containers.
The blast stirred memories of war in a city that had been relatively calm in recent years.
Beirut suffered more than its share of explosions — car bombings, shelling and airstrikes — during a prolonged civil war and fighting between Israel and the militant group Hezbollah.
But if the latest explosions were found to have been caused intentionally, they would shatter a prolonged stretch of relative calm in the Lebanese capital.
Less than a week ago, Israel said it had thwarted a raid by a “terrorist squad” from Hezbollah, the Shiite group that is part of Lebanon’s government, in a disputed border area. Israeli military officials said there was an exchange of gunfire, which Hezbollah denied.
Israeli military officials say Hezbollah has planted many rockets in southern Lebanon that could threaten northern Israel. But In recent years, Hezbollah has refrained from killing Israelis while Israel has largely avoided killing Hezbollah fighters in Syria, where they are fighting on the Syrian government’s side.
Both Israel and Hezbollah have sought to avoid a war that could devastate Lebanon and Israel.
An Israeli military spokeswoman declined to confirm or deny any involvement by Israel in the explosion on Tuesday.