|Vast areas in Tabasco state have been submerged [AFP]|
Half a million people have been left homeless and one person has been killed after the Mexican state of Tabasco suffered its worst flooding in more than 50 years.
Nearly the entire low-lying southern state has been submerged after a week of heavy rain, leaving residents trapped on rooftops and clinging to lamp-posts on Friday.
Felipe Calderon, the Mexican president, earlier described the flooding as one of the worst natural disasters in Mexico's history.
Of the estimated 900,000 people whose homes have been flooded, damaged or cut off, about 300,000 have yet to be rescued.
Weather forecasters have predicted more rainfall in the coming days.
Nearly all services, including drinking water and public transportation, have been shut down in the state capital Villahermosa.
Troops organised the evacuation of Villahermosa's city centre on Thursday after residents refused to leave their flooded homes amid reports of looting.
Rescue services were struggling to deal with the size of the damage.
Andres Granier, the governor of Tabasco, said potable water supplies had been exhausted in Villahermosa.
Dozens of people anxious about relatives and friends gathered outside government offices seeking assistance.
Others waded despondently through waist-deep water or wandered along highways leading out of the capital.
"We lost everything," said Manuel Gonzalez, whose house was flooded.
"I left without one peso in my pocket and I can't find my siblings."
The state of Chiapas, which borders Tabasco to the south, also reported serious flooding. Officials there estimated more than 100,000 people had been affected.
The flooding has raised fears of possible outbreaks of cholera and other waterborne diseases.
Mauricio Hernandez, a federal health official, said: "With so many people packed together there is a chance that infectious diseases could spread."
Officials tested for 600 suspected cases of cholera, a waterborne sickness which is often fatal but has not been reported in Mexico for at least six years, but none was positive, according to Hernandez.
The government has also sent 20,000 Hepatitis A vaccinations and was giving booster shots to children to prevent outbreaks, Hernandez said.
But medical care was difficult because at least 50 of the state's hospitals and medical centres had flooded.
Mexico geared up to help the flood victims, with morning entertainment shows switching airing calls for aid and banks remainng open to accept donations, even though Friday was the national Day of the Dead holiday.
Calderon called Mexicans to contribute bottled water, canned goods, nappies and other vital supplies to donation centres around the country.
"Nobody can stand around with his arms crossed," he said. "We can't and won't abandon our brothers and sisters in Tabasco."