While that remained the official death toll, Prime Minister Giuseppe Conte said from Genoa that the number would rise.
A 50-metre high section of the bridge, including a tower that anchored several stays, crashed down with as many as 35 vehicles driving on it in torrential rain. Huge slabs of reinforced concrete plunged onto two warehouses, train tracks and a riverbed.
The government of the Liguria region tweeted that 19 bodies had already been identified and 15 people had been admitted to hospital, nine in critical condition.
More than 400 people were evacuated from buildings near or below the still-standing section of the bridge. The collapse appeared not to have killed anyone beneath the bridge, only people driving over it, the civil protection agency said.
Firemen heard voices under the rubble and pulled out seven survivors.
Within hours of the disaster, the anti-establishment government that took office in June said the collapse showed Italy needed to spend more on its dilapidated infrastructure, ignoring EU budget constraints if necessary.
Aerial footage showed trucks and cars stranded on either side of the 80-metre long collapsed section of the Morandi Bridge, built on the A10 toll motorway in the late 1960s.
An official for the civil protection agency said there had been 30 cars and five to 10 trucks on the section that fell.
Some 300 firemen were working in the wreckage, using sniffer dogs to try to locate survivors, along with 400 police.