Citing witnesses, news agency MTI reported late on Saturday that a petrol bomb was thrown at a house in Tatarszentgyorgy, 65 km (40 miles) southeast of Budapest, near the scene of an attack on Monday which killed a man and his five-year-old son.

But the preliminary findings of an investigation into the cause of Saturday's fire revealed no wrongdoing, police and disaster relief authorities said.

"Arson can be ruled out with almost complete certainty," said Ferenc Zoltan, head of the Pest County Disaster Relief Directorate. He said initial findings indicated the source of the fire may have been a malfunctioning electric radiator.

Attacks on Hungary's Roma population, which makes up about 5-7 percent of its 10 million people, have increased with the global financial crisis. Some analysts say the Roma have become a target for frustration over slow economic growth. A far-right group has blamed the Roma for what it says is rising crime.