Three corpses were found on Tuesday shortly after the fire and explosion rocked the plant owned by Enel Green Power, part of Enel Group, on the shores of the artificial Lake Suviana.
Two other workers remain unaccounted for.
Divers recovered the two bodies from the ruins of a turbine hall nine levels - 40 metres or so - below the lake.
One of them was named as Adriano Scandellari, who was 57 and worked for Enel Green Power.
The cause of the accident has not been established and Italian prosecutors have launched an investigation, as is mandatory in such cases.
Bologna Chief Prosecutor Giuseppe Amato said the probe would look into “procurement and subcontracting”, an issue the unions say is a major factor.
“These are sub-contract deaths,” said Bologna CGIL Secretary Michele Bulgarelli.
“It is a day of anger because, after the shock, I think that yesterday’s statement and press conference by Enel Green Power was absurd, unacceptable and unworthy of a civilised country.
“The offloading of responsibility in the procurement chain sees it list three or four [contractor] companies.
“But up to today we have no official information about which companies employed the employees [involved].”
Enel Green Power CEO Salvatore Bernabei stated that “we do not deserve this kind of statement” and that “there is no subcontracting chain”.
On Wednesday, he had said that top companies had been chosen for the work being done at the plant.
“In order to carry out this technological upgrade of supply, assembly and testing, we had chosen the best companies in the field of electricity and hydroelectricity: Siemens, Abb, Voith,” Bernabei said.
“When I turn to a contractor, that contractor is synonymous with prestige and seriousness.
“You have to ask the contractors [about the work subcontracted out], who, in turn, can turn to other specialists, because the work we are doing here is work that can only be done by specialists.”
The deaths have compounded already widespread concerns expressed by trade unions about workplace safety in Italy, after a series of fatal accidents in factories and building sites.
Enel staff went on strike for eight hours over the issue on Thursday, while workers in other sectors held a previously announced four-hour stoppage and demonstrated in towns and cities across Italy.
Protesters held banners saying “Adesso basta!” (“Enough now!”) to make their point that it was time to stop fatal accidents in workplaces.
Unions said that more than half of Enel workers had joined the strike, but the company put the figure much lower, at less than nine per cent.
AAP / ANSA
