A Greek minister has said there were "serious indications" that the fires had been started deliberately. Experts have blamed haphazard and unlicensed building for the high death toll, which climbed to 82.
Greek authorities said on Thursday they suspected arson was behind the devastating forest fires that killed at least 82 people near capital Athens.
"We have serious indications and significant signs suggesting the criminal actions of arson," Civil Protection Minister Nikos Toskas told a news conference. He said police had testimonies to that effect, but did not elaborate.
Toskas said satellite image analysis of the deadly fires that broke out on Monday on the east and the west sides of Athens indicated that both had been set in multiple places within a short time frame.
Fifteen fires had started simultaneously in three areas around Athens, raising suspicions among authorities. US surveillance aircraft were being used to gather footage to try to determine the causes of the fires.
Wildfires near populated areas in Greece are often blamed on arsonists believed to be targeting forest land for development, but arrests are rare.
Sad aftermath of Greek fires
Most casualties were found at the resort town of Mati, some 30 kilometers (18 miles) east of Athens.
A group of experts from the University of Athens' Faculty of Geology and Geo environment blamed the layout of the town for the high death toll.
The group said the haphazard and unlicensed building, with scant provision for fire safety, had acted like a "fire trap" as they blocked access to the sea.
"How is it possible to have so many lives lost and not investigate who is responsible for such town planning chaos," Infrastructure Minister Christos Spirtzis said.
About 300 firemen and volunteers were still combing the area on Thursday for dozens still missing.
DW's Charlotte Chelsom-Pill, who is in Mati, said people from across the region have donated food and clothes to those rendered homeless by the fires.