Emergency workers respond after a four-story apartment building collapsed following a gas explosion in Sicily, Italy on December 12, 2021. At least three people were killed and six are missing. Photo: AFP

Rescuers in Sicily prepared late on Sunday for a second night of searching for possible survivors trapped under the rubble of collapsed buildings after a massive explosion probably caused by a gas leak. 

Three people have been confirmed dead by Sicily's regional civil protection unit in the disaster that caused four residential buildings to topple to the ground on Saturday night in the southern town of Ravanusa. 

Although two women were recovered alive from the debris early on Sunday after being found by sniffer dogs, six people remained unaccounted for as night fell. Rescuers had not heard signs of life from under the rubble since morning, authorities said. 

"The search continues to the bitter end. We are searching in the hope of finding our six fellow citizens still alive," Ravanusa Mayor Carmelo D'Angelo said, according to Italian news agency AGI. 

"We have the whole country on our side, and the best human and technological resources are in place. Hope will not be extinguished."

The blast, which occurred around 1930 GMT on Saturday, leveled four structures, including a four-story apartment building, in the central residential district of Ravanusa, a town of nearly 11,000 inhabitants, according to the civil protection unit. 

Television images broadcast throughout the day showed a mass of concrete rubble, wooden beams and mangled steel in a large empty space, with neighboring buildings charred and damaged. 

Firefighters had worked to extract the largest, heaviest materials from the site of the collapsed buildings in order to better access levels below, said Luca Cari, spokesman for Italy's national firefighters. 

"The problem is the huge quantity of rubble that we have to deal with to be able to advance," Cari told RaiNews24 television.  

"The work is meticulous... we're moving debris but with great care in order to avoid provoking new collapses," he said in a statement. 

Earlier in the day, Cari said it had been hours since the rescue teams had heard signs of life under the rubble.  

AFP