Quote from the link. I like the CNN part.
“Many buildings were damaged by the explosion, including the headquarters of former Prime Minister Saad Hariri and CNN’s bureau in the city.”
That reinforces the Hezbollah likelihood as the perps.
Saad El-Din Rafik Al-Hariri
Maj. Gen. Abbas Ibrahim, the director general of Lebanese intelligence, dismissed the fireworks explanation as "ridiculous," attributing the blast to confiscated highly-explosive materials being stored at the local port. Local media reported that the confiscated material was sodium nitrate.
Ibrahim said though that he would not preempt the investigation.
A red-orange cloud, the color of which could be explained by nitrates, lingered over part of the city after the explosion. The extent of the damage is currently unknown, but local reports indicate that while the blast was focused on the port area, there was extensive, widespread damage across the city, as well as an unknown number of casualties.
The national news agency reports that "the number of casualties is countless." Wednesday has been declared a national day of mourning.