Here is what we know about the Beirut explosions

A pair of explosions, the second much bigger than the first, struck the city of Beirut on Tuesday evening, killing at least 100 people, wounding more than 4,000 and causing widespread damage.

The second blast sent a billowing, reddish plume high above the city’s port and created a shock wave that shattered glass for miles. On Wednesday morning, despite a huge search operation, dozens were still missing in the city, the capital of Lebanon on the eastern coast of the Mediterranean Sea.

As the authorities piece together what happened, here is a look at what we know and what we don’t.

What caused the explosions?

The exact cause remains undetermined. The first blast may have been in a fireworks warehouse at the port. Officials say the second, more devastating explosion most likely came from a nearby 2,750-ton stockpile of ammonium nitrate, a highly explosive chemical often used as fertilizer, which Prime Minister Hassan Diab said had been stored in a depot for six years.

Investigators will try to determine whether the blasts were accidents or intentionally triggered. Beirut was engulfed in civil war from 1975 to 1990 and has seen bombings and conflict since then, raising fears of a possible return of violence. But Maj. Gen. Abbas Ibrahim, the head of Lebanon’s general security service, warned against speculating about terrorism before the facts were known.

The 2,750 tons of ammonium nitrate that exploded are believed to have come from a Russian-owned vessel that stopped in Beirut while it was sailing in 2013 from Georgia to Mozambique. The ship was abandoned, and the cargo is believed to have been offloaded to the port’s warehouses, the site of the explosion Tuesday.

Where did it happen?

The blasts caused severe damage to buildings, warehouses and grain silos in the port, a central storage location for grain and a critical link in the country’s supply chain for goods including food and medicine.

The grain silos that were damaged or destroyed store 85% of the country’s grain, and the authorities said that the wheat that had survived was now inedible.

The port, in the north of the city, handled 60% of the country’s overall imports, according to S&P Global.

Beyond the industrial waterfront, the explosions tore through popular nightlife and shopping districts and densely populated neighborhoods. More than 750,000 people live in the parts of the city that were damaged, and at least 300,000 had been displaced as of Wednesday.

Even before the explosions, Lebanon had been suffering from a series of crises, including the plunging value of its currency, an influx of refugees from neighboring Syria and the coronavirus pandemic. Since last fall, waves of protesters have taken to the streets to vent anger with Lebanon’s political elite over what they consider the mismanagement of the country.

How big were the blasts?

The second explosion was like an earthquake, witnesses said, and was felt in Cyprus, more than 100 miles away. The seismic waves that the explosion caused were equivalent to a 3.3-magnitude earthquake, according to the U.S. Geological Survey.

Ammonium nitrate explosions have caused a number of disasters before. A ship carrying about 2,000 tons of the compound caught fire and exploded in Texas City, Texas, in 1947, killing 581 people. About two tons of the chemical were used in the 1995 terrorist bombing of the federal building in Oklahoma City, which killed 168 people.

More recently, an explosion at a factory in the southern French city of Toulouse killed 31 people in 2001. In 2013, 15 people were killed in an explosion at a West Fertilizer Co.plant in Texas; and in 2015, more than 150 people were killed at one of China’s busiest seaports, Tianjin, after hundreds of tons of ammonium nitrate, among other chemicals, exploded.

How bad was the damage?

Ceilings collapsed, walls and windows were blown out and debris was found far as two miles from the port. Cars were flipped, and rubble from shattered buildings filled city streets.

The governor of Beirut, Marwan Aboud, told reporters on Wednesday that half of the city had been damaged, with the financial toll expected to surpass $3 billion.

Several hospitals, already strained from the coronavirus pandemic, were damaged, four of them so severely that they could not admit patients, doctors said. At the Bikhazi Medical Group hospital in the center of the city, a ceiling fell on some patients, the hospital director said. Many doctors and nurses were also killed in the blast.

Hamad Hasan, Lebanon’s health minister, said in a televised address that government warehouses had been damaged and that the country was “running short of everything necessary to rescue” and treat victims.

What comes next?

Diab, the prime minister, has vowed that the explosions won’t “fly by without accountability,” but in a country marred by decades of corruption, many in Lebanon were skeptical that any high-profile figures would face consequences.

The investigations are likely to focus on why thousands of tons of ammonium nitrate were stored at the port, and who made the decision to let a highly combustible substance sit there for years.

The Lebanese authorities have placed Beirut port officials who had overseen storage and security since 2014 under house arrest, the minister of information said Wednesday.