ROME (AP) — Divers in northern Italy have recovered the last two bodies of workers killed by an explosion that collapsed and flooded several levels of an underground hydroelectric plant, bringing to seven the number of confirmed dead, officials said Friday.

The explosion Tuesday at the Enel Green Power plant, in northern Bologna province, occurred at depth of some 40 meters (130 feet) below water level.

Four other workers who were wounded in the massive blast are hospitalized and two of them are still in serious condition, officials said.

Divers who worked for more than two days to recover the victims' bodies likened the scene to an underwater earthquake-struck building.

The blast at Enel Green Power’s Bargi plant happened during work to increase the plant’s efficiency, the company said in a statement. A fire broke out when a turbine exploded on the eighth floor below the surface, flooding the floor below. The cause was still unknown.

Local prosecutors have opened a probe into the accident.