Israel carried out its operation against Hezbollah on Tuesday by hiding explosive material within a new batch of Taiwanese-made pagers imported into Lebanon, according to American and other officials briefed on the operation.

The pagers, which Hezbollah had ordered from Gold Apollo in Taiwan, had been tampered with before they reached Lebanon, according to some of the officials. Most were the company’s AR924 model, though three other Gold Apollo models were also included in the shipment.

Independent cybersecurity experts who have studied footage of the attacks said it was clear that the strength and speed of the explosions were caused by a type of explosive material.