The simultaneous explosion of thousands of pagers used by Lebanese militia Hezbollah on Tuesday was the result of an unprecedented weaponization of a wireless paging system, in which rigged devices detonated upon receiving a coded signal transmitted by radio frequency.

At least 20 people were killed and another 450 were wounded, the Health Ministry said, in this apparent second attack.

Israel launched a series of strikes on Hezbollah targets Thursday as the war against the Lebanon-based group widened in the wake of two consecutive days of deadly explosions triggered in wireless devices.

Lebanese officials say more handheld devices exploded a day after thousands of pagers carried by Hezbollah members blew up in an attack blamed on Israel.

A company based in Hungary was responsible for manufacturing the pagers that exploded in an apparent Israeli operation targeting Hezbollah, another firm said Wednesday. The attack

Taiwanese company Gold Apollo said Wednesday that it authorized its brand on the pagers that exploded in Lebanon and Syria in an apparent Israeli operation targeting Hezbollah’s communications network but that another company based in Budapest manufactured them.

Over two days, pagers and walkie-talkies used by Hezbollah detonated, wounding and even crippling some fighters, but also maiming civilians and killing at least two children.

Israel bombed Hezbollah strongholds in southern Lebanon on Thursday, piling pressure on the militant group after two waves of explosions targeted its communications systems, killing 37 people.