AMATRICE, Italy — Italian authorities are vowing to investigate whether negligence or fraud in adhering to building codes played a role in the high death toll in last week’s earthquake.

They also called for efforts to ensure organized crime doesn’t infiltrate lucrative construction contracts to eventually rebuild much of the picturesque towns leveled in the disaster.

Meanwhile, rescue workers pressed on with the task of recovering bodies from the rubble, while hopes of finding any more survivors virtually vanished more than four full days after the powerful quake.

Over the past two days, they found six more bodies in the rubble of Hotel Roma in Amatrice, the medieval hill town in mountainous central Italy that bore the brunt of destruction and loss of life. They recovered three and by late Sunday were still working to retrieve others that were hard to reach.

It wasn’t clear if those six were included in the overall 290 death toll given by authorities. The Civil Protection agency, which combines the figures it receives from different provinces affected by the quake, said the number is lower than the previous toll of 291 dead because of a correction in the numbers from the province of Rieti, where most of the victims died.

The quake that struck before dawn Wednesday also injured nearly 400 people as it flattened three medieval towns near the rugged Apennines. Prosecutor Giuseppe Saieva, based in the nearby provincial capital of Rieti, said the high death toll “cannot only be considered the work of fate.”

“The fault lines tragically did their work and this is called destiny, but if the buildings had been built like in Japan they would not have collapsed,” Saieva said in comments carried by Italian media.

Investigations are focusing on a number of structures, including an elementary school in Amatrice that crumbled despite being renovated in 2012 to resist earthquakes at a cost of $785,000. With schoolchildren’s summer vacations in their final weeks, the school wasn’t yet in use.