At least three people were killed on Tuesday when a fire and explosion occurred at the plant owned by Enel Green Power, part of Enel Group (ENEI.MI), opens new tab, near the town of Camugnano, about 60 km(40 miles) from Bologna.
The deaths have stoked 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 will stage a previously planned four-hour stoppage.
"Unfortunately the conditions for recovery are not good," said Bologna mayor Matteo Lepore, who was at the scene.
"They are very difficult - the depth of this blast is very deep, they are talking of 70 metres (230 feet) ... The fire is now out. Divers are also helping," he added.
One of the missing workers was from Voith Hydro, a German company that was one of the contractors that had been working on improvements to the plant, Voith said.
"The facts are still unclear. We ask for your understanding that we cannot make any further statements at this time," said Kristine Adams, vice president global corporate communication at Voith.
A general view shows the Enel hydroelectric power plant, after a fatal explosion and fire, in Bargi, Italy, April 10, 2024. REUTERS/Claudia Greco Purchase Licensing Rights,opens new tab
The power plant had been undergoing efficiency works, which Enel Green Power entrusted in late 2022 to three primary companies, Siemens Energy (ENR1n.DE), opens new tab, ABB and Voith.
"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.
The board of Enel Group issued a statement on Wednesday to express its condolences to families of victims and solidarity with all those involved.
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.
A spokesperson for Siemens Energy also expressed the company's shock and sympathy for those affected
