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 U.

U.N. peacekeepers in Lebanon urged immediate de-escalation as hostilities rumbled on at the Lebanese-Israeli border on Friday, following Israel's most intense airstrikes in nearly a year of conflict with the Iran-backed Hezbollah.

For millions of Lebanese, this week's mass explosion of pagers and walkie-talkies, with its bloody aftermath, is painfully similar to the horrific explosion four years ago of haphazardly stored ammonium nitrates that tore through Beirut's port,

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Here are the unanswered questions. Some early speculation suggested that the pagers could have been targeted by a complex hack that caused them to explode. But that theory was quickly dismissed by experts.