The blast occurred at a dam on Lake  Suviana, 43 miles from the city of Bologna, at 6:00 AM PST on Tuesday. The plant is located 100 ft below sea level. The area is now completely flooded.

Five people had been seriously injured. They are known to have suffered from severe burns following the explosion and were flown to nearby hospitals via helicopter. Two men have been taken to the ICU according to local media. The three victims of the disaster -all contractors- were aged between 36 and 73. According to unconfirmed reports, state two were from southern Italy and one was Romanian.

It is thought that a fire broke out when a turbine exploded on the eighth floor below the surface, causing the floor below to have been flooded.

One of the divers involved in the search and rescue operation told the Italian newspaper, La Repubblica, that he had managed to reach the seventh floor below the surface, but could not rescue the three people that are still trapped further down.

Bologna Mayor Matteo Lepore, who visited the scene on Tuesday evening, said that the underground search teams’ conditions were “really complicated.” He noted that it was one of the worst work tragedies to occur in Italy’s recent history.

The mayor of the nearby town of Camugnano, Marco Masinara, said, “Everyone around here cares about the plant which has never been a source of danger but one of employment.” He said that the man who was most seriously injured was a young man in the area in the process of starting a family.

The city’s chief prosecutor, Giuseppe Amato, told Italian media an investigation would be launched once the plant was safe and the missing people were found.

The cause of the accident is yet to be determined, but what happened is likely to create concerns expressed by trade unions about workplace safety in Italy. Two of the country’s largest unions were already due to hold four-hour-long nationwide strikes on Thursday to protest the issue.

Lake Suviana is an artificial lake located in the Appenine Mountain Range near Bologna. The lake was formed following the construction of a dam in 1932.

The powerplant is owned by the company Enel Green Power, a subsidiary of the Italian energy giant Enel. The company expressed its deepest condolences and closeness to all of the victims and their families and said that while there was no evidence that the dam had been damaged, the power plant had stopped production.