Lebanon's Environment and Health Ministries have warned residents in neighbourhoods near Beirut's port to wear masks and stay indoors amid concerns a massive silo may partially collapse.

A fire in the silo's northern block has been smouldering for the past two weeks due to the 725 tonnes of grain inside it fermenting in the hot weather.

The ministries anticipate dust from construction waste and some fungi from rotting grains in the silos could heavily disperse for up to 24 hours if the structure falls.

The silos withstood the impact of the devastating blast in August 2020, acting as a shield to protect Beirut's western neighbourhoods from the explosion.

The blast was caused by hundreds of tonnes of ammonium nitrate — a highly explosive material used in fertilisers — that had been improperly stored for years at the port's warehouse.

The explosion tore through the Lebanese capital, and killed over 200 people and wounded over 6,000 more.

A French civil engineer who volunteered for the government-commissioned team of experts warned that a collapse of the north block was inevitable as it was already tilting after the port blast.

The engineer, who has been monitoring the silo for two years via sensors, said the fire accelerated the building's tilting. 

AP