Italian President Sergio Mattarella is due to preside over a state funeral for 18 of the victims of Tuesday's bridge collapse in Genoa.
Mr Mattarella and Prime Minister Giuseppe Conte will lead mourners at the ceremony at a hall in the city.
So far 38 people are confirmed to have died in the disaster and five are still unaccounted for.
Some families are reportedly staying away from Saturday's ceremony because of anger at the government.
The collapse of a section of the Morandi motorway bridge and the deaths of those crossing in vehicles have led to a fierce debate in Italy about the nation's infrastructure.
The government has set up a commission to examine the causes of the disaster and one member speculated on Friday that a broken cable rod was "a serious work hypothesis".
The bridge, which was constructed in the 1960s, has cables running directly from the deck to the top of the towers.
Families gather for funeral
On Friday, grieving relatives gathered at the hall in Genoa where rows of coffins were laid out for Saturday's state funeral.
Family members embraced and prayed and placed photographs and flowers on the coffins of their loved ones.
Saturday's ceremony coincides with a national day of mourning and will be led by the city's archbishop, Cardinal Angelo Bagnasco.
But a number of families chose not to take part and are holding private burials elsewhere in Italy.