A preliminary investigation by Lebanese authorities into the communications devices that blew up in Lebanon this week found that they were implanted with explosives before arriving in the country, according to a letter sent to the UN Security Council by Lebanon's mission to the UN.

Additional explosions linked to electronic devices caused more deaths and injuries a day after pagers used by Hezbollah exploded, wounding thousands.

Lebanon’s health ministry said Wednesday that at least 20 people were killed and 450 others wounded by exploding electronic devices in multiple regions of the country. The explosions came a day after an apparent Israeli attack targeting pagers used by Hezbollah killed at least 12 and wounded nearly 3,

The Hezbollah militant group said it is conducting a "security and scientific investigation” into the explosion of pagers across Lebanon on Tuesday.

Walkie-talkies and solar equipment exploded in Beirut and other parts of Lebanon on Wednesday in an apparent second wave of attacks targeting devices a day after pagers used by Hezbollah blew up, state media and officials for the militant group said.