What could have caused the deadly pager explosions in Lebanon that harmed thousands?

Pagers used by hundreds of members of Hezbollah exploded almost simultaneously in Lebanon and Syria Tuesday, killing at least 12 people – including two children – and wounding thousands more.

Hezbollah leader Hassan Nasrallah previously warned the group's members not to carry cellphones, saying they could be used by Israel to track the group's movements. As a result, the organization uses pagers to communicate.

Hezbollah said it was carrying out a "security and scientific investigation" into the causes of the blasts and said Israel would receive "its fair punishment."

What could cause pagers to explode?

The first theory is battery overheating. Diplomatic and security sources speculated that the explosions could have been caused by the devices' batteries detonating, possibly through overheating.

In an interview with China Media Group, military expert Du Wenlong suggested that pagers could be remotely manipulated. He explained that this could be achieved by embedding malicious software that would endow the program with the power to inflict tangible harm. Utilizing this malware, the devices could be coerced into malfunctioning, resulting in conditions such as overheating, accelerated operation and electrical overload, all of which could culminate in the devastation of the hardware. 

Many others, however, have said that Israel might have infiltrated the supply chain for Hezbollah's pagers.

Several experts who spoke with The Associated Press explained how the explosions were most likely the result of supply-chain interference.

Very small explosive devices may have been built into the pagers prior to their delivery to Hezbollah, and then all remotely triggered simultaneously, possibly with a radio signal.

By the time of the attack, "the battery was probably half-explosive and half-actual battery," said Carlos Perez, director of security intelligence at the U.S.-based TrustedSec.

A former British Army bomb disposal officer explained that an explosive device has five main components: a container, a battery, a triggering device, a detonator and an explosive charge. "A pager has three of those already," said the ex-officer, who spoke on condition of anonymity because he now works as a consultant with clients in the Middle East. "You would only need to add the detonator and the charge."

The New York Times reported that Israel hid explosive material within a new batch of the pagers before they were imported to Lebanon, citing American and other officials briefed on the operation.

Doubts

Several experts who spoke with Reuters said they doubted the battery alone would have been enough to cause the blasts.

Paul Christensen, an expert on lithium-ion battery safety at Newcastle University in Britain, said the damage seemed inconsistent with past cases of such batteries failing.

"What we're talking about is a relatively small battery bursting into flames. We're not talking of a fatal explosion here ... my intuition is telling me that it's highly unlikely," he said.

Another reason to doubt the explosions were caused by overheating batteries is that typically only a fully charged battery can catch fire or explode, said Ofodike Ezekoye, a mechanical engineering professor from the University of Texas at Austin.

"Below 50 percent (charge) ... it will generate gases and vapor, but no fires or explosions. It is highly unlikely that everyone whose pager failed had a fully charged battery," he said.

Israeli intelligence forces have previously placed explosives in personal phones to target enemies, according to the 2018 book "Rise and Kill First." 

Reuters reported that hackers have demonstrated the ability to inject malicious code into personal devices, causing them to overheat and explode in some instances.

(With input from AP and Reuters)