The broader Evros region is a popular route for migrants crossing the river from Turkey into Greece, Reuters reported.
"Given that there have been no reports of disappearances or missing residents from the surrounding areas, the possibility that these are people who entered the country illegally is being investigated," the fire brigade said. "Searches throughout the entire area where the fire broke out are ongoing."
Another body thought to belong to a migrant was found on Monday.
Earlier on Tuesday, dozens of hospital patients, including newborn babies, were evacuated onto a ferry as hundreds of firefighters struggled to contain the blaze that broke out near Alexandroupolis on Saturday.
It spread quickly, fanned by gale force winds, sending plumes of smoke above the city and turning the night sky red.
Fires also broke out on Tuesday near the capital Athens, where a blaze on the city's outskirts, on the foothills of Mount Parnitha, was threatening homes. An operation was underway to evacuate nuns from Kleiston Monastery, the fire brigade said.
Another blaze burned uncontrolled in the industrial town of Aspropyrgos. More than 120 firefighters and nine aircraft were fighting the blazes near Athens.
By early Tuesday, authorities said 65 patients at the University Hospital of Alexandroupolis had been evacuated as a precaution onto a ferry in the port.
Fourteen more people were evacuated by a coastguard vessel from a beach near the village of Makri.
SKH/PR