[UPDATED] BREAKING: Massive explosion in Beirut rocks buildings for hundreds of feet; 'very high number of casualties' — source remains unclear

A major explosion in Lebanon's capital of Beirut shattered windows and rocked buildings for hundreds of feet, according to reports.

What's happening?

Disclose shared a video on Twitter, captioning it, "Massive explosion in Beirut. Al-Mayadeen reports the explosion in Beirut is not an act of terrorism according to preliminary information. But holy moly ... what is the cause of something like this?!"

The outlet also reported "VERY HIGH number of casualties reported by the Lebanon health minister as a result of the explosion in Beirut (Sky News)."

The explosion took place Tuesday, according to The Guardian, and its source is not clear at the time of this writing.

The outlet reports that the explosion "rocked central Beirut" and "shattered windows, knocked down doors, and shook buildings several hundred feet away."

"An enormous cloud of smoke could be seen from across the city and witnesses said there were reports of a fire and several small explosions at the port preceded the large blast after 6pm on Tuesday," the outlet continued.

The BBC reported that there were several explosions — one smaller one following the massive blow that shook buildings for blocks.

The outlet reported on "unconfirmed reports" of a second blast, and points out that "A UN tribunal is due to issue its verdict in the trial of four suspects in the murder by car bomb of [Lebanon ex-PM Rafic Baha El Deen Al ]Hariri."

The four suspects are reportedly members of Iranian-backed Hezbollah group.

Reports have emerged that the possible second explosion reportedly took place at the Hariri residence in Beirut.

The verdict is due on Friday.

Local state-run media report that the explosion source was a "major fire at a warehouse for firecrackers near the port." The report said large numbers of people were wounded.

CNN reported that "[m]any buildings were damaged by the explosion, including the headquarters of ... Hariri."

Eyewitnesses also say that residences as far as 10 kilometers away were damaged due to the blast.

Internet outages abound

Reports are also emerging about a "significant internet outage" following the blast.

A tweet read, "Confirmed: Real-time network data show significant internet outage in #Lebanon following reports of blast near #Beirut impacting ability to contact eyewitnesses; circumstance and cause remain unclear; incident ongoing; see live report for updates."

Update, 8/4/2020, 1:03 PM ET:

A CNN producer said that the scene at local emergency rooms was "chaotic" following the blast.

"Some people had broken limbs, some showered with glass," producer Ghazi Balkiz told the outlet.

"I walked in, I saw a few people lying on the floor — doctors trying to put IVs into them. A couple of people were passed out," he added.

The Lebanese Red Cross also reports thousands of calls to local emergency numbers.

More and more videos continue to flood social media channels, showing all angles of the horrific explosions.

Update 8/4/2020 1:36 PM ET:

The Guardian reports that the medical situation in the city is quickly disintegrating.

"A doctor at St Joseph's hospital, less than 2km (1.2 miles) from the blast, said dozens of injured people were being brought for treatment but were unable to be received because the hospital had been destroyed," the outlet reported.

"They're bringing people to the hospital but we can't treat them," the doctor told the outlet. "They're leaving them outside in the street. The hospital is broken, the ER is broken."

Update 8/4/2020 1:52 PM ET:

CNN reports that eyewitnesses call the aftermath of the explosion apocalyptic.

Bachar Ghattas told CNN's Becky Anderson, "You can see injured people all over the streets in Beirut, glass all over the place, cars are damaged, it is like an apocalypse."

"Beirut port is totally destroyed," he added."We don't have a port."

CNN also reported that the blast could be felt 150 miles away from Lebanon.

Israeli officials told Reuters that it denied involvement in the explosion.

"Israel has nothing to do with the incident," the official said on condition of anonymity.

CNN reports that at least 400 people have been hurt because of the explosion, citing the account of a local registered nurse.

Update 8/4/2020 2:19 PM ET:

The Guardian reports that Lebanon Interior Minister Mohamed Fehmi reportedly told the MTV Lebanon channel that the massive explosion appeared to have been caused by "huge quantities of ammonium nitrate" being stored at Beirut port, where the explosion took place.

Update 8/4/2020 2:30 PM ET:

Marwan Abboud, the governor of Beirut, tearfully told journalists on Tuesday that the country is devastated by the blast.

"[Firefighters] came to fight the fire, and then they vanished," he says. "We don't know where they are. We're here to look for them.

"This reminds me of what happened in Japan, to Hiroshima and Nagasaki," he added. "I've never seen damage of this size and width, and so catastrophic. This is a national catastrophe. This is a problem for Lebanon, and we don't know how we're going to get out of it.

Israel's Foreign Minister Gabi Ashkenazi denied all suggestions that Israel could have been responsible for the explosion, saying he had "no reason not to believe the reports from Beirut that this was an accident."

Update 8/4/2020, 3:37 PM ET:

Beirut Health Minister Hamad Hassan told reporters that, at the time of this writing, least 50 people were confirmed to be dead as a result of Tuesday's massive explosion.

More than 2,750 people were injured.

French President Emmanuel Macron announced that the country would be sending "rescue and aid" to Lebanon in response to the medical crisis.

"I express my fraternal solidarity with Lebanese people after the explosion that caused so many casualties and so much damage tonight in Beirut," he said in a tweet. "France stands by Lebanon's sides. Always. French rescue and aid is on its way."

Lebanon's prime minister, Hassan Diab, declared Wednesday to be a national day of mourning for the victims of the blast.

Diab insisted that the warehouse from which the blast apparently originated was the subject of concern dating back to 2014.

"I promise you this catastrophe will not pass without accountability. The people who are responsible will pay a price," Diab said.

This is a developing story and will be updated as events warrant