1,320 kgs of fireworks were found in 120 boxes in a warehouse during a search of the port.
Before the explosion, Lebanon was already grappling with its worst economic crisis in recent history, worsening poverty and decades of state corruption and mismanagement.
Since the explosion, Lebanon's police have arrested 25 people, including the port's head.
He also said the army inspected 143 containers at the port that he said were found to hold other flammable material.
The civil defense said in a statement that firefighters had extinguished the flames on Friday morning after working through the night.
Tens of thousands of Lebanese signed a petition calling for the restoration of the French mandate over the country
Questions are being raised about why a serious fire broke out again, blackening the sky.
Stores of oil and tires were what caught fire, according to a source in the Lebanese military.
"Always in search operations like this, you can neither lose hope nor absolutely say there is hope," George Abou Moussa, director of operations in Lebanon's civil defense, told Reuters.
"How many people could have survived if there had been a state and rescue operations ready?"