The northern section of the grain silos damaged two years ago by a blast at the Beirut port collapsed early on Tuesday after warnings the structure was leaning too far to stay up.
The crash sent a cloud of brown-grey dust billowing over the waterfront, the LBCI television station reported. There were no immediate reports of injuries.
The huge explosion at the port on August 4, 2020, killed more than 220 people and gutted the northern section of the grain silos, leaving wheat and corn spilling out in the sun.
Recently, a fire had been smouldering in the silos for weeks, which officials said was the result of summer heat igniting fermenting grain left rotting.
Part of the structure collapsed on July 31 and another section fell on August 4, the second anniversary of the blast.
On Sunday, the health ministry said dust samples from around the port showed that the air contained high amounts of common mould, which would not be dangerous unless inhaled in large quantities over a long period of time.
Ukrainian President Volodymyr Zelenskyy marked Independence Day on Sunday alongside Canadian Prime Minister Mark Carney, who said Ukraine would receive more than C$1 billion ($723 million) in military aid from a previously announced package next month.
Israeli planes and tanks pounded the eastern and northern outskirts of Gaza City overnight Saturday to Sunday, destroying buildings and homes, residents said, as Israeli leaders vowed to press on with a planned offensive on the city.
The Pentagon is working on plans to deploy the US military to Chicago as President Donald Trump says he is cracking down on crime, homelessness and undocumented immigration, the Washington Post reported on Saturday.
Thousands of Australians joined pro-Palestinian rallies on Sunday, organisers said, amid strained relations between Israel and Australia following the centre-left government's decision to recognise a Palestinian state.
North Korean leader Kim Jong Un supervised the firing of new air defence missiles to test their combat capability, state media KCNA reported on Sunday.