What we know about the massive explosion in Beirut that killed at least 135, injured thousands

Residents of Beirut are surveying the damage Wednesday after a massive explosion rocked the Lebanese capital, killing at least 135 people, wounding thousands and causing widespread damage.

Videos shared online showed a dark cloud rising from the port, what normally might be expected from an industrial-area fire, followed by an explosion creating a massive white cloud that enveloped the area. A moment later, the shock wave hit.

As residents of the city search for missing relatives, bandage their wounds and retrieve what’s left of their homes, the Lebanese government said it is putting an unspecified number of Beirut port officials under house arrest pending an investigation and declared a two-week “state of emergency,” effectively giving the military full powers during this time.

'Still covered in blood': Beirut, Lebanon, searches for survivors of massive explosion

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How many people were killed?

At least 135 people were killed and more than 5,000 wounded, Reuters reported citing an interview with Lebanon's health minister on Al Manar.

An official with the Lebanese Red Cross, George Kettaneh, warned that the death toll could rise further. Health Minister Hassan Hamad had earlier reported at least 70 deaths.

The United Nations Interim Force in Lebanon said some of its naval peacekeepers were seriously injured in the blast. Bangladesh said 21 members of its Navy were wounded, one critically. Italy, one of the top contributors to the UNIFIL mission, said one of its soldiers was wounded.

How much damage was caused?

Elegant stone buildings, fashionable shopping districts and long stretches of the famed seaside promenade were reduced to rubble within seconds of Tuesday’s blast.

VIDEOS: One explosion, seven different angles

Hangars around the port were completely toppled and much of the downtown area was littered with damaged vehicles and debris that had rained down from the shattered facades of buildings.

It was the worst, most destructive single explosion to strike the country.

The force shook buildings, which were hit again by the shock wave that blew out windows, sending shards of glass flying through the air. One of the UN ships docked in the port was damaged, according to UNFIL.

The blast severely damaged numerous apartment buildings, and Beirut's city governor Marwan Abboud said up to 300,000 people had lost their homes and authorities are working on providing them with food, water and shelter, Al-Jazeera reported.

The government said public schools will be opened to host those who lost their homes and the minister of tourism will also work on opening some hotels for use by those who lost their homes. It also promised compensation for the victims.

Smoke was still rising from the port Wednesday, where a building of silos was half destroyed, spilling out mounds of grain. Drone footage shot by The Associated Press showed that the blast tore open a cluster of grain silos that estimates suggest housed some 85% of the country’s grain.

"I was sitting on the stairs ... next thing I remember I was on the ground covered with shattered glass and people screaming," said Shehadeh Khalaf, 67, who said he was helped at the hospital but left because there were so many more people in dire need. "I'm still covered in blood."

The blast, which struck shortly after 6 p.m. local time with the force of a 3.5 magnitude earthquake, according to Germany’s geosciences center GFZ, followed a fire that broke out in the city's port area, based on multiple videos from the scene.

What caused the blast?

The cause of the explosion has yet to be officially determined, but Abbas Ibrahim, chief of Lebanese General Security, said it might have been caused by highly explosive material that was stored at the port after it was confiscated from a ship. The material was identified as ammonium nitrate in a tweet on the Lebanese presidential account.

"It is unacceptable that a shipment of ammonium nitrate estimated at 2,750 tons has been present for six years in a warehouse without taking preventive measures that endanger the safety of citizens," Prime Minister Hassan Diab said according to the tweet.

Videos showed an orange cloud over Beirut's port after the explosion, which is consistent with a nitrate-related explosion. Explosives experts and video footage suggested the ammonium nitrate may have been ignited by a fire at what appeared to be a nearby warehouse containing fireworks.

What is ammonium nitrate?

Ammonium nitrate is an industrial chemical commonly used as fertilizer for plants and can be used to make explosives, according to the National Institutes of Health. It does not readily burn, but will do so if contaminated with combustible material. It's also an oxidizer, meaning that it draws oxygen to a fire and can make it more intense.

“You need extreme circumstances to set off an explosion,” Gabriel da Silva, a senior lecturer in chemical engineering at the University of Melbourne, told the Guardian.

Ammonium nitrate will produce produce toxic gases that are made of nitrogen and oxygen when burned. While the chemicals in the air should dissipate quickly da Silva told the outlet that lingering pollutants can cause problems if they acidify rain.

In a domestic terrorism case that shook America, Timothy McVeigh killed 168 people by creating a bomb from two tons of ammonium nitrate mixed with fuel oil to blow up the Alfred P. Murrah Federal Building in Oklahoma City in 1995.

The Beirut explosion recalled the twin blasts that killed at least 50 and injured more than 700 in the Chinese port of Tianjin in 2015. Investigators found that blast was triggered when a flammable compound caught fire in the August heat and the flames then spread to illegal stores of ammonium nitrate.

Investigation and international aid coming soon

Lebanon's Supreme Defence Council recommended that a committee investigate the explosion and present its findings within five days to punish to those responsible, Al-Jazeera reported. The Council also recommended declaring a two-week state of emergency in Beirut and giving the military security responsibility.

State prosecutor Ghassan Oueidat ordered security agencies to start an immediate investigation and collect all reports and letters related to the materials stored at the port as well as lists of people in charge of maintenance, storage and protection of the hangar.

Though the cause of the explosion has yet to be officially determined, President Donald Trump called it a "terrible attack" based on the suspicions of U.S. generals he did not name.

There was no evidence the explosion was an attack. Instead, many Lebanese blamed it on decades of corruption and poor governance by the entrenched political class that has ruled the tiny Mediterranean country since the civil war.

Israel, which has seen years of intermittent conflict with Lebanon, particularly and recently with Hezbollah, denied any involvement and offered humanitarian medical aid. France and the United Nations special coordinator also offered humanitarian assistance.

History: Even before explosion, Lebanon teetered toward collapse

'Terrible attack': Trump says massive explosion in Beirut appears to be an attack but local officials are still investigating

Contributing: The Associated Press, Jordan Culver and Nadia Al Faour, USA TODAY

Follow N'dea Yancey-Bragg on Twitter: @NdeaYanceyBragg

This article originally appeared on USA TODAY: Beirut explosion: What we know about the massive blast that killed 135