ROME (AP) — An accident at a supermarket construction site in the Italian city of Florence on Friday killed at least three workers and left two others missing, local officials said.

The accident happened when a reinforced concrete beam toppled over a slab of a pre-fabricated building, which then collapsed. Local authorities said rescue teams were searching for the missing and that they feared the death toll could rise further.

Three other workers who were pulled out from the rubble of the collapsed building were taken to local hospitals and were later said to be in serious but not life-threatening condition. Tuscany region’s president, Eugenio Giani, said there were about 50 people on the site at the time of the accident, but only eight workers were reportedly involved in the collapse.

The supermarket under construction is part of Italy's Esselunga chain.

Giani told Italian TV SkyTg24 that the accident could have been even more tragic, as a school bus with children was passing near the site at the time. He added that the tragedy would "push all of us to commit strongly to avoid something similar ever happening again.”

Two street cleaners who arrived on the site shortly after the accident said they could hear the cries of injured workers calling out for help.

The building site has been cordoned off and formally seized by investigators. Later on Friday, Florence's public prosecutor office opened a probe, for now without naming suspects, for “culpable collapse and manslaughter,” Italian news agency ANSA reported.

Italy’s three largest unions — CGIL, CISL and UIL — called for a “general strike” in Tuscany following the accident to demand better safety measures.

“No more deaths at work,” said their joint statement, denouncing a surging number of accidents on Italian workplaces amid difficult and risky work conditions.

In 2021, the last year for which there is official data from the statistics agency Eurostat, Italy registered 601 workplace deaths. It was the second-highest figure in the European Union after France that year.

Italian Prime Minister Giorgia Meloni expressed her condolences on X, formerly Twitter, and said she was following the developments “with apprehension.”

The president of Esselunga, Marina Caprotti, expressed her grief for the accident and said that the company will be available to cooperate with magistrates to shed light on what caused the collapse.

Florence’s Mayor Dario Nardella proclaimed a day of mourning in the city on Saturday.