At least 73 people died and about 3,700 were injured Tuesday after a massive explosion in downtown Beirut that shattered windows and caused apartment balconies to collapse, Lebanese Health Minister Hamad Hassan said.While the cause of the explosion was not immediately known, local media citing the country's authorities said that ammonium nitrate stored in the port may have triggered the blast.Related coverage:Rusted gas pipe likely behind deadly explosion in northeastern Japan1 dead, 18 hurt in Fukushima explosion, gas leak suspectedThe explosion is the biggest in Beirut in years, Reuters s…READ FULL ARTICLE