Lebanon authorities impose state of emergency after at least 100 people were killed and 4,000 wounded in a massive explosion

CNN's senior international correspondent Ben Wedeman went inside a home overlooking the port where Tuesday’s massive explosion took place in Beirut. The home was inhabited by an elderly couple.

Looking out through the walls of the home that have collapsed, Wedeman describes the state of the warehouse that exploded. What was simply dry ground before, Wedeman says, is now a crater, with water flowing into the area.

The Lebanese government has committed to conducting a transparent investigation into the explosion, but Wedeman says it is “scant consolation” to the families of those killed, injured and missing.

Beirut's governor said in an interview earlier today that at least 300,000 people have been displaced from their homes by the blast.

Go inside the home damaged by the explosion:

An aerial view of Beirut. AFP/Getty Images

Lebanese authorities declared Beirut a “disaster city" on Wednesday, according to Lebanon State-run NNA news, citing a statement released by the country’s Minister of Information Manal Abdel Samad Najd.

A state of emergency has been declared in Beirut for two weeks, Najd said in the statement, adding this could be extended.

The country’s Council of Ministers made the two decisions on Wednesday in an “extraordinary session” headed by President Michel Aoun and in the presence of the prime minister.

It was also decided in the extraordinary session "to instruct the High Relief Commission to secure shelter for families whose homes are no longer fit for housing, open schools and hotels to receive citizens, and request from the security services to ensure Not to tamper with the crime scene," the statement said.

A nurse in Beirut takes care of three babies in a damaged hospital on August 4. Bilal Jawich/Xinhua/Getty Images

A nurse pulled three babies out of a hospital rocked by the massive explosion in Beirut on Tuesday, a photographer who took her picture told CNN Arabic.

Photojournalist Bilal Jawich said he was at home on the outskirts of Beirut when the blast, which has left at least 100 dead and thousands injured, rocked the Lebanese capital.

"I followed the smoke until I reached the port of Beirut," he said, explaining that "professional intuition" took him to Al Roum hospital, in the Ashrafieh district. The area has been left devastated by the blast.

"However, the nurse looked like she possessed a hidden force that gave her self-control and the ability to save those children," Jawich said. "People stand out amidst these violent and dark and evil circumstances and this nurse was up to the task."

Jawich said the nurse told him later that evening that she was in the maternity ward when the blast hit. She said she had been knocked unconscious, and when she came around “found herself carrying these three children,” he told CNN Arabic.

Not everyone in the hospital was so lucky. George Saad, emergency preparedness and disaster manager for the hospital told CNN that some 12 patients, two visitors and four nurses died in yesterday's incident, while two remain in critical condition. Some 80% of the hospital had been damaged, along with 50% of its equipment, he said.

WATCH:

Drone footage captured by CNN this morning showed the destruction left in the wake of Tuesday’s deadly explosion in Beirut.

At least 100 people were killed in the blast, and the death toll could rise as many more people are reported missing. At least 4,000 people were injured in the explosion.

Watch the footage:

We're still not exactly sure what caused the deadly explosion in Beirut yesterday, but Lebanon's prime minister said an investigation would focus on an estimated 2,750 metric tons of the explosive ammonium nitrate stored at a warehouse.

So what is ammonium nitrate? Also known as AN, it's a compound of ammonia and nitrogen, is a highly volatile material used in agricultural fertilizers and bombs.

Disasters involving AN are rare, considering the US uses millions of tons of it every year in fertilizers, according to the Environmental Protection Agency. "Pure" solid AN is quite stable, but if the compound is mixed with any contaminants, even in small traces, the mixture becomes much more prone to detonation  — which is why there are normally stringent government guidelines for how to treat and store it properly.

For instance, AN shouldn't be stored with any fuel, organic materials, chlorides or metals, said the guide — all potential contaminants. The EPA guidelines also recommend fire resistant walls in the storage unit, noncombustible flooring, and — crucially — controlled temperatures.

AN doesn't burn, but if exposed to heat, it can melt — which releases combustible toxic gases that can cause an explosion. It's even more dangerous if there is a large supply of AN all stored together, because once a small section of AN begins to melt and explode, the resulting heat can set off the rest of the supply.

Some history: One of the worst disasters in US history involving a form of ammonia occurred in April 1947 when a ship loaded with ammonium nitrate caught fire while docked in Texas City. The fire caused an explosion and additional fires that damaged more than 1,000 buildings and killed nearly 400 people, according to the website of the Texas Historical Association.

For perspective, that explosion was triggered by 2,300 US tons (about 2087 metric tons) of ammonium nitrate, according to US Homeland Security.

And the 1995 Oklahoma City Bombing, a US domestic terror attack that killed 169 people and injured 467, used only two US tons (1.8 metric tons) of ammonium nitrate.

August 5. Planet Labs, Inc.

This satellite image from Planet Labs, Inc, showed the destruction left in the wake of yesterday's deadly explosion in Beirut.

At least 100 people were killed in the blast, and the death toll could rise as many more people are reported missing. At least 4,000 people were injured in the explosion.

For comparison, here's what the port area looked like before the blast:

May 31. Planet Labs, Inc.

The Lebanese cabinet has ordered that “officials” involved in the Beirut port explosion be placed under house arrest “in the coming days,” the Lebanese Minister of Displaced People Ghada Shreim said without providing further details.

An injured person sits by a restaurant on August 5. Patrick Baz/AFP/Getty Images

Every single business in Beirut has been affected by yesterday's deadly blast, Lebanon's Economy Minister Raoul Nehme said.

“There is not one apartment in Beirut that wasn’t impacted, not one businesses that wasn’t impacted – whether the storefront of the goods” he said. 

”The impact on the economy is massive and the port has been practically erased,” Nehme told CNBC Arabia in an interview Wednesday, adding it was too soon to fully gauge the scale of the damage on the economy. 

He said the government’s priority was to secure people’s basic necessities – mainly food but also supplies to help repair the extensive damage to homes and infrastructure across the city. 

Turkey is sending search and rescue teams, health care workers, medical supplies and other urgent humanitarian aid to help in the aftermath of the blast in Beirut, according to the Turkish foreign ministry.

Turkey is also planning on setting up a field hospital, the ministry said in a written statement.