LAKE SUVIANA, Italy - Hopes of finding survivors of an accident at a power plant in northern Italy are dwindling, firefighters said on Wednesday, as rescuers searched for four people missing in an area of the plant where water was rising rapidly.

At least three people were killed on Tuesday after a fire and explosion occurred underground at the hydroelectric power plant owned by Enel Green Power, part of Enel Group, near the town of Camugnano, about 60 km (37 miles) from Bologna.

The deaths are fuelling concerns already expressed by trade unions about workplace safety in Italy after a series of fatal accidents in factories and building sites.

Enel workers plan to strike for eight hours over the issue on Thursday, while workers in other sectors nationwide are holding a previously planned four-hour stoppage.

"The rescuers' hope is always to find people alive. The scenario we see does not make us believe much in these hypotheses, but I repeat that we are also accustomed to miracles," Luca Cari, a fire brigade spokesperson, said on Wednesday.

Cari said that the situation was very difficult, due to the water rising quickly inside the power plant, which was built underground on one of the banks of Lake Suviana.

The rescuers were working mainly with divers, but they still did not have details on the potential causes of the accident, he added.

UPGRADE WORKS

The power plant had been undergoing efficiency works, which Enel Green Power entrusted in late 2022 to three primary companies, Siemens Energy, ABB and Voith, Enel's subsidiary said in a statement.

"This is a tragedy... a tragedy that hits our company, our community and our sector," Enel Green Power CEO Salvatore Bernabei told reporters at the scene.

"This is not the time to talk about the causes of the accident, we are focusing our energy on helping the families (of those affected) and helping the fire fighters to find the missing people."

Enel Green Power said that testing of a first group of turbines had been completed in recent days and that work was ongoing to test a second group at the time of the accident.

Bernabei said Siemens Energy, ABB and Voith were among the leading companies in the field for such upgrade works.

In a statement to Reuters, ABB expressed its condolences to the victims and wished the injured a swift recovery.

"ABB is aware of the presence of an ABB employee onsite when the incident occurred. ABB will provide information as soon as available," it added.

There was no immediate comment from Siemens Energy or Voith. REUTERS