The government, long accused of endemic corruption, resigned on Monday but will remain in a caretaker position until a new cabinet is formed.
Protesters have been calling for the wholesale removal of what they see as a corrupt ruling class they brand as responsible for the country's woes, including an economic meltdown that has ravaged the currency, paralysed banks and sent prices soaring.
Officials have said the blast could have caused losses of $15 billion, a bill Lebanon cannot pay, given the depths of the financial crisis that has seen people frozen out of their savings accounts since October amid dollar scarcity.
President Michel Aoun has promised a swift and transparent investigation into the blast and said the probe would look into whether it was negligence, an accident or external factors.
Reports emerged that Aoun and now-resigned Prime Minister Hassan Diab were warned in July about the warehoused ammonium nitrate.