A massive explosion rocked Beirut with the force of an earthquake, followed by a shock wave that blew out windows and caused widespread damage across the Lebanese capital on August 4, 2020. Photo: www.rediff.com

Injured residents flooded hospitals, pushing them past capacity. Medical officials pleaded for blood donations.

The blast followed a fire that broke out in the city's port area, based on multiple videos from the scene. 

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.

"I've met with some of our great generals and they just feel it was," Trump said at a White House press conference where he offered condolences and assistance to the Lebanon people. "It was a bomb of some kind."

Abbas Ibrahim, chief of Lebanese General Security, said the blast might have been caused by highly explosive material that was stored at the port after it was confiscated from a ship.

In a tweet on the Lebanese presidential account, the material was identified as ammonium nitrate, citing Prime Minister Hassan Diab as saying, "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."

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.

Videos showed an orange cloud over Beirut's port after the explosion, which is consistent with a nitrate-related explosion. 

The force shook buildings, which were hit again by the shock wave that blew out windows, sending shards of glass flying.

Beirut Gov. Marwan Abboud called it a "national catastrophe," and the prime minister declared a day of mourning, according to CNN. 

“It resembles what happened in Japan, in Hiroshima and Nagasaki. That’s what [it] reminds me of. In my life, I haven’t seen destruction on this scale," Abboud said of the mushroom cloud.

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.

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

The blast, which occurred shortly after 6 p.m. local time, was followed by the wail of ambulance sirens through streets covered in debris.

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. The second was the more powerful of the two, equivalent to an estimated 21 tons of TNT.

Over the past few decades, Beirut has endured bloodshed from suicide bombings, armed conflict with neighboring Israel and a civil war.