Hundreds of pagers exploded in Lebanon, Syria. Here’s what we know.

Authors: Wyatte Grantham-Philips, Michael Biesecker, Sarah el Deeb and Sarah Parvini | Associated Press

NEW YORK — In a sophisticated remote attack, pagers used by hundreds of Hezbollah members exploded almost simultaneously Tuesday in Lebanon and Syria, killing at least nine people — including an 8-year-old girl — and injuring thousands more.

A U.S. official said Israel informed the United States about the operation — which involved detonating small amounts of explosives hidden in pagers — on Tuesday after it ended. The person spoke on condition of anonymity because he was not authorized to discuss the information publicly.

The Iranian-backed militant group blamed Israel for the deadly explosions, which affected an unusually wide range of people and showed signs that it was a long-planned operation. Details about how the attack was carried out are largely uncertain, and investigators did not immediately say how the pagers were detonated. The Israeli military declined to comment.

Here’s what we know so far.

Why were pagers used in the attack?

Hezbollah leader Hassan Nasrallah has 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.

A Hezbollah official told The Associated Press that the exploding devices were from a new brand that the group had not used before. The official, who spoke anonymously because he was not authorized to speak to the press, did not name the brand or supplier.

Nicholas Reese, a lecturer at the Center for Global Affairs at New York University’s School of Professional Studies, explains that smartphones carry a greater risk of communications being intercepted compared to simpler technology such as pagers.

Such attacks will also force Hezbollah to change its communications strategy, said Reese, who previously worked as an intelligence officer, adding that survivors of Tuesday’s explosions would likely throw away “not just pagers, but phones, and leave behind tablets and other electronic devices.”

How could sabotage cause pagers to explode?

Even though a U.S. official confirmed that it was a planned Israeli operation, multiple theories emerged Tuesday about how the attack could have been carried out. Several experts who spoke to The Associated Press explained that the explosions were most likely the result of interference with the supply chain.

Very small explosive charges may have been incorporated into the pagers before being delivered to Hezbollah, and then all were detonated simultaneously, probably via a radio signal.

At the time of the attack, “the battery was probably half explosive and half real battery,” said Carlos Perez, director of security intelligence at TrustedSec.

The former British Army sapper explained that an explosive device consists of five main parts: a container, a battery, a triggering device, a detonator and an explosive charge.

“The pager already has three of these,” said the former officer, who asked not to be identified because he now works as a consultant for Middle Eastern clients. “You just need to add a detonator and a charge.”

After security footage allegedly showing a pager detonating on a man’s hip in a Lebanese market emerged on social media Tuesday, two ammunition experts offered testimony supporting a U.S. official’s statement that the explosion was most likely the result of a small explosive device.

“When you watch the footage, the force of the detonation is similar to that of an electrical detonator alone or one with an extremely small explosive charge,” said Sean Moorhouse, a former British Army officer and explosive ordnance disposal expert.

That’s a sign of state actor involvement, Moorhouse said. He added that the Israeli intelligence agency, Mossad, is the most obvious suspect with the resources to carry out such an attack.

NR Jenzen-Jones, a military weapons expert who is director of Australia’s Armament Research Services, notes that Israel has been accused of carrying out similar operations in the past. Last year, the AP reported that Iran accused Israel of trying to sabotage its ballistic missile program by using faulty foreign parts that could explode, damaging or destroying the weapons before they could be used.

How long did this operation take?

Planning an attack of this scale would take a long time. The exact details are still unclear, but experts who spoke to the AP offered estimates ranging from several months to two years.

The sophistication of the attack suggests the perpetrator had been gathering intelligence for a long time, Reese explained. An attack of this caliber requires building relationships to gain physical access to the pagers before selling them; developing the technology to be embedded in the devices; and finding sources who can confirm that the targets were carrying pagers.

And it’s likely that the infected pagers appeared normal to their users for some time before the attack. Elijah J. Magnier, a Brussels-based veteran and senior political risk analyst with more than 37 years of experience in the region, said he has spoken to Hezbollah members and survivors of Tuesday’s pager attack. He said the pagers were acquired more than six months ago.

“The pagers worked perfectly for six months,” Magnier said. The cause of the explosion, he said, was an error message sent to all the devices.