The Lebanese army said the fire is at a warehouse that stores oil and tires.
Frustration is high, with the state almost nowhere to be seen and promised international help slow in coming.
Mustapha Adib was named before French President Emmanuel Macron arrived in Beirut to push for reforms as the country faces several threats to its stability.
The FBI will assist with an investigation into the massive blast in Beirut that killed more than 170 people.
The explosion has fueled popular outrage against the country's top political leaders and security agencies, and led to the resignation of the government on Monday.
Anti-government protests erupted in Beirut after a warehouse explosion killed at least 160 people and injured thousands.
Protests against the country's ruling elite have erupted in Beirut following the massive blast in a Beirut Port warehouse.
Activists in Lebanon blame politicians' corruption and negligence for the blast that killed nearly 160 and left thousands injured.
A wave of destructive energy shot across Lebanon’s capital.
More than 130 people died in an explosion in the Lebanese port city.