BEIRUT (AP) — A day after angry protests decrying the handling of the investigation into the massive explosion at Beirut's port last August, Lebanon’s president said Wednesday there will be no political cover for anyone accused in the case.

The blast on Aug. 4 was caused by the ignition of hundreds of tons of ammonium nitrate at the port for years. The highly explosive fertilizer was stored there with the knowledge of top government officials.

It still wasn't clear what exactly caused the explosion and an investigation by a state-appointed judge has been riddled by charges of political interference. The first investigator, who charged senior officials with negligence, was removed from the case.

The delays have frustrated the public, particularly amid reports that most of the Lebanese leadership, including the president, had knowledge of the explosive material stored in the port. They did little to store it safely or to alert civilians in the area of its presence.

Beirut’s port and parts of the city were devastated in the ensuing massive explosion that killed over 200 people and injured hundreds more.

Angry protests outside the house of the interior minister of the caretaker government Tuesday lasted for hours. Families of the victims and explosion survivors held a mock funeral and burial outside his home. Protesters scuffled with security forces guarding the building, who fired tear gas to disperse the crowd. Dozens of protesters and security forces were lightly injured.

Interior Minister Mohammed Fehmi had rejected a request by the new lead investigator to remove immunity for one of the most senior security officials accused in the port case — the head of general security Abbas Ibrahim, allowing him to be questioned.

President Michel Aoun said the investigation into the explosion is ongoing, saying “there will be no political cover for anyone who was negligent or guilty.” However, Aoun did not address critics who said that Fehmi obstructed the investigation by granting immunity to Ibrahim.

Aoun's comments came during a meeting with Patrick Durel, the visiting envoy of the French President Emmanuel Macron.

Aoun also approved Aug. 4 as a day of mourning, declaring it a national holiday nearly a year after the blast. Families of the victims have been campaigning for this recognition.