The northern block of the silos collapsed in a huge cloud of dust after what sounded like an explosion. It was not immediately clear if anyone was injured.

The 50 year-old, 48-meter tall giant silos withstood the force of the explosion two years ago, effectively shielding the western part of Beirut from the blast that killed over 200 people, wounded more than 6,000 and badly damaged entire neighbourhoods.

In July, a fire broke out in the northern block of the silos due to fermenting grains. Firefighters and Lebanese Army soldiers were unable to put out the fire which continue smouldering for weeks, releasing odours into nearby cities.

The environment and health ministries last week issued instructions to residents living near the port to stay indoors in well-ventilated spaces.

Emmanuel Durand, a French civil engineer who volunteered for the government-commissioned team of experts, told the Associated Press that the northern block of the silo has already been tipping since the day of the blast, but the fire has weakened its frail structure, accelerating its collapse.