ROME (AP) — Architect Renzo Piano has offered a new bridge design for his beloved hometown of Genoa to replace the one that collapsed last month, killing 43 people, saying it must be built to last 1,000 years and be "simple, solid ... but not banal."

Piano joined city and regional officials on Friday to present the plans for the new bridge, which officials hope to have operational by November 2019. Piano said it would likely be built in steel and recall the shape of a ship in a nod to Genoa's maritime tradition.

"A bridge that falls is terrible, because a bridge is a symbol," Piano told a press conference in Genoa. "Bridges shouldn't fall. They can't fall. They're a symbol that unifies, that brings things together."

Prosecutors this week announced 20 people were under investigation for the disaster, which also forced some 600 people from their homes underneath the bridge, and that the list could grow.

Italian news reports have documented evidence, including technical studies that show officials were well aware of the bridge's fragility and had scheduled maintenance work, but took no measures to reduce or divert traffic in the meantime.

Among those under investigation are officials from the private company that controls the bridge, Autostrade per l'Italia; including its chief executive, Giovanni Castellucci, who was on hand Friday alongside Piano to present the new bridge plans.

Castellucci has said the company takes responsibility for the bridge's collapse, but is not guilty.

Liguria regional president Giovanni Toti said he hoped to persuade the government to skip the lengthy public bidding process that would normally accompany such a huge public works project, saying Genoa cannot wait.

He said crews must work quickly but securely to remove the remains of the reinforced concrete Morandi bridge and give Genoa a new bridge that memorializes the pain of the disaster, unifies the now-divided city and "looks to a great future."

Demolition and rebuilding plans, however, are very much on hold since the disaster site is still off-limits and an active crime scene.

Piano, who is so revered in Italy that he was named a senator-for-life by the Italian president, has said he was donating his design to his hometown. But his offer has sparked a backlash, with some professional groups saying his "offer" was robbing other architects of the chance to bid for the project.

Consumer lobby Codacons said Friday that Piano's gift was fine, but urged the government to follow the regular norms for competitive bidding for the project.

Autostrade's board has already approved an initial 500 million euros ($576 million) in funding to help victims and finance the new bridge.