There are "serious indications of arson" in one of several Greek wildfires that killed more than 80 people this week, authorities said Thursday.

Nikos Toskas, deputy minister for citizen protection, said the belief is based on satellite images and ground inspections by police and fire officials at the scene of a deadly blaze that started in the town of Penteli in east Attica.

More than 15 fires broke out on three fronts in that part of southern Greece on Monday afternoon, according to government spokesman Dimitris Tzanakopoulos, who described the challenge to firefighters as unprecedented.

The mayor of the municipality where more than 80 people lost their lives to wildfires has admitted that mistakes were made in the response to the crisis, telling CNN that no evacuation order was given and that the scale of the fire was “underestimated.”

Vagelis Bournos, mayor of Rafina-Pikermi, said that although weather conditions including very strong winds had played a major role, human error was partly to blame for the deaths, citing the lack of a warning as well as longer-term problems including poor urban planning and the impact years of austerity had on public services.

But the mayor also defended the decision not to evacuate Mati and the surrounding coastal villages, where hundreds of homes were gutted in the blaze that tore through the area on Monday.

“Citizens do not follow evacuation plans but they stay behind to protect their households,” he said.

“Of course there is anger due to the fact that there are victims. But the same people who are angry now, when the evacuation order would have been issued, they would have stayed back and tried to protect their houses. So victims would still be there, a smaller number, but still.”

A number of bodies were found in cars and close to the sea, however, suggesting that many residents did attempt to flee. Hundreds more made it to the beaches and rocky coastline, some waiting in the sea for hours before being rescued.

Demetres Karavellas, director general of WWF Greece, which has warned for years of the deadly threat posed by wildfires and often advises local authorities on how to regenerate areas after fires, described the mayor’s reasoning as “a lame excuse.”

“People were trying to leave, people were trying to get out,” he told CNN on Thursday.

Bournos admitted that there was a window of time in which an evacuation order could have been issued, but it was missed. By the time the blaze was close to Mati, “practically, there could not have been an evacuation,” he said. “The decision would have had to have been made a couple of hours earlier.”

“We could have made better decisions for sure,” he said.

A Mati resident who did not want to be named out of fear he would get in trouble with the local authorities told CNN on Wednesday that locals had been requesting preparedness plans for wildfires for several years to no avail. “This was an accident waiting to happen,” he said.

Bournos confirmed that residents had made such requests and said that plans had been produced by local volunteer firefighting organizations, but only for smaller-scale scenarios.

As the global climate continues to change, this type of fire will become more likely, Karavellas warned.

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