"Breaking: Israel nukes Beirut," says an image in an August 4, 2020 Facebook post.
Also Read: Did Israeli PM Benjamin Netanyahu Claim Responsibility For Beirut Blasts?
The image appears to be a screenshot of a headline from the "Veterans Today" website, which advertises itself as "Serving the Clandestine Community."
Other claims that the Beirut blast was nuclear appear on Facebook here, here and here, Instagram here and here, and Twitter here.
The August 4 explosion at Beirut's port was devastating, killing more than 110 people and leaving thousands wounded. But it was not nuclear.
Lebanon's Prime Minister Hassan Diab said 2,750 tons of the agricultural fertilizer ammonium nitrate that had been stored for years in a portside warehouse exploded, sparking "a disaster in every sense of the word."
The government has said it is seeking house arrest for all officials involved in storing the highly-explosive substance, which came to Lebanon aboard a ship called the Rhosus that was bound for Mozambique.
Despite this, President Donald Trump claimed US generals had told him that the blast appeared to have been caused by a "bomb of some kind."
Experts meanwhile said evidence does not indicate that the blast was nuclear.
"It doesn't look anything like a nuclear explosion," Jeffrey Lewis, a nonproliferation expert at the Middlebury Institute of International Studies at Monterey, told AFP by phone.
"If this were a nuclear explosion, there would have been a bright flash of light, which there wasn't," and "generally speaking, nuclear explosions are much, much, much larger than this," he said.
Lewis also noted that the reddish-brown color of the cloud that rose over Beirut following the blast is "very typical of ammonium nitrate."
"There's nothing about it that looked nuclear, and a lot of things about it that looked like an ammonium nitrate explosion."
Also Read: Unrelated And Dated Images Being Shared As Aftermath Of Beirut Blast
Vipin Narang, an associate professor of political science at MIT who specializes in nuclear weapons and proliferation, agreed.
"It was an intense blast, and it is a tragedy for the people of Beirut. But it was not nuclear," Narang told AFP by email.
There was "no double flash. The double flash is the characteristically unique feature of a nuclear detonation: an intense flash of light which dims as the shockwave obscures the fireball, but then brightens as the shockwave dissipates," he said.
Additionally, "nuclear mushroom clouds are not red," as was the cloud in Beirut.
The explosion comes during the collapse of Lebanon's economy -- yet another problem with which the crisis-hit country now has to contend.