BEIRUT, Sept 18 (Reuters) - Hand-held radios used by armed group Hezbollah detonated on Wednesday across Lebanon's south in the country's deadliest day since cross-border fighting erupted between the militants and Israel nearly a year ago, stoking tensions after similar explosions of the group's pagers the day before.

Two people from Taiwanese companies were questioned as part of a probe into pagers that exploded while being used by Hezbollah operatives in Lebanon, investigators said Friday, as top officials insisted the devices were not from the island.

The deadly simultaneous explosions triggered by hundreds of pagers carried by Hezbollah members in Lebanon have thrust a little-known Taiwanese electronics manufacturer into the global spotlight, after its damaged products were identified in images following the attack.