Weeks of torrential rains have unleashed flooding in huge swaths of southern Mexico, forcing tens of thousands of people from their homes.

Tens of thousands more are sleeping on their roofs, refusing to abandon their possessions even as the rivers around them rise rapidly.

Authorities on Tuesday started releasing 2,000 cubic meters (71,000 cubic feet) of water per second from four damns in the region that have reached capacity. That caused several rivers to overflow.

Hipolito Hernandez swiftly hauled many of his belongings onto his roof as the Rio Carrizal jumped its banks and flooded dozens of home in the farming community of Sauces in the Gulf coast state of Tabasco.

Hernandez, 38, gave some of his possessions to relatives who went to shelters but he stayed put. In 2007, he lost everything when he left his home during flooding that left 1 million homes underwater and killed 33 people.

"We are waiting to see what happens, we can still withstand this flood," Hernandez said

The flooding has affected all four southernmost Mexican states: Tabasco, Veracruz, Chiapas and Oaxaca. People in the region are accustomed to severe flooding every year, and the government often struggles to persuade residents to leave dangerous zones.

In Tabasco, the homes of more than 124,000 people have been severely flooded. More than 187,000 hectares of crops belonging to 20,000 people have been lost.

But only 2,000 people in the state are in shelters.

"They are refusing to leave their homes and they don't want to go to shelters because they have a culture of living with water," Tabasco Gov. Andres Granier said during a meeting with President Felipe Calderon, who flew over the affected areas Tuesday and walked through some flooded towns.

Granier warned Calderon the situation could become even worse than in 2007 as record rainfall is expected.

"What worries me is that the worst is yet to come for Tabasco," Granier said. "The state and these people cannot keep suffering these problems each year, or live in permanent uncertainty."

Already, authorities said the region has received twice the amount of rainfall that normally falls during the season, which does not officially end until November.

The government has built relief ditches and other infrastructure in the past years to ease the annual flooding in southern Mexico. Calderon acknowledged more needs to be done, but said the flooding would be much worse this year without the government's advances.

He pointed to emergency levees made of concrete and dirt erected on the banks of the Grijalva, which has swelled rapidly and threatens to flood the state capital, Villahermosa. A few outlying neighborhoods were severely flooded, however.

In neighboring Veracruz state, flooding has forced 200,000 people from their homes over the past weeks, although some have started returning.

"They evacuated us when the water was up to our waists, but the water had already broke all the doors of our house," said Angelica Martinez Galindo, the mother of a 3-year-old girl who had to flee Tlacotalpan, a colonial town in Veracruz state that UNESCO named a World Heritage site.

She said at least 20 men stayed behind in her neighborhood to try to salvage possessions.

Clara Luz Montalvo said she resisted leaving her home in El Juchil because her 82-year-old mother didn't want to move. When they finally were forced to flee, they were nearly swept away by floodwaters and had to be rescued by marines on a boat.

"It was a very serious situation. My mother can hardly walk and I have a sister who is disabled. I don't know what I would have done if it hadn't been for the government, the marines," said Montalvo, waiting her turn at a food line at a shelter in Veracruz city.

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Associated Press writer Miguel Angel Hernandez in Veracruz, Mexico contributed to this report.