The Greek government said satellite image analysis and ground inspections provided "serious indications" the fire, which broke out on Monday and hit coastal villages popular with tourists in the Attica area, was set deliberately, the Independent reports.
The fires killed at least 82 people, with rescue crews and volunteers continuing to search on land and at sea for more victims.
"We have serious indications and significant findings of criminal activity concerning arson," public order minister Nikos Toskas said on Thursday.
"We are troubled by many factors, and there have been physical findings that are the subject of an investigation."
Before Toskas’s news conference, the mayor of the area where the blaze broke out said it might have been sparks from a severed electricity pylon cable, the Independent reports.
The speed with which the flames spread took many by surprise, especially in the coastal resort of Mati.
One Belgian national and one Irish national are among those confirmed dead.
Even those on beaches were not safe, as flames burned trees and vegetation.
The Queen offered her condolences to Greece in a statement on Thursday.
“Prince Philip and I offer our deepest sympathies to the people of Greece in the wake of the devastating fires in Attica and across Greece,” she said.
“Our thoughts and prayers are with the family and friends of the victims of this terrible tragedy and to all those who have lost their homes.
“I pay tribute to the courage and dedication of the Greek emergency services and the volunteers that have provided support.”
Greece specialist Olympic Holidays has pledged its support to help the country recover in the wake of the fires.
Through its Children’s Charity Fund, the operator will help Greek-based charity Desmos.org which is helping to meet the immediate needs of those affected.
The organisation is providing food, hygiene products, water and clothing to those in need and now Olympic Holidays’ customers can give their support, by adding a £1 donation to their booking fee which will be matched by the operator.
Money raised will go directly to Desmos.org’s GoFundMe page.
