Hundreds of thousands of people have been left homeless as severe floods continue to rage through Mexico's southern state of Tabasco, in the country's worst natural disaster for decades.

Rescue workers and police were out in force on Saturday helping flood victims, as fears grew of a looming health crisis.

The floods have affected more than one million residents, half of Tabasco's population, but only one death has been reported.

In the southern state of Chiapas at least four people died after rain-swollen rivers burst their banks, damaging 5,000 homes and 16 bridges.

Flood waters looked ready to recede on Saturday, but forecasters said that with a cold front due to move into the area there could be more rain in store.

Many were set to spend another night on their rooftops, with tens of thousands already crammed into emergency shelters struggling to provide enough hot meals and dry beds.

One group stranded on a roof held a banner reading: "Enough. There are children, pregnant women, sick women. Send the police."

Health officials have voiced concerns about looming health risks from open sewage and the spread of disease-carrying mosquitoes.

Dengue, cholera and diarrhoea outbreaks are now real possibilities, they said.

Jose Angel Cordova Villalobos, the health minister, admitted that shelters were jammed and said authorities were planning to open new emergency facilities at sports arenas and possibly at a bull ring.

During the crisis, about 69,000 people have managed to get into about 600 government shelters, Beatriz Zavala, the federal social development minister, said.

Many fled flooding in Villahermosa, the state capital, for less affected areas.

Mauricio Hernandez, one resident fleeing the city, said: "We are leaving because we cannot live like this. We don't have any water, and the shelters are full."

Thousands of people have fled Tabasco into the neighbouring states of Chiapas and Veracruz seeking refuge.

But many others remained despite the flooding, refusing to leave for fear that looters would take all their possessions.

Looting

Around 1,000 people reportedly overran a shopping centre in Tabasco, overwhelming police posted in the area, and stealing items including televisions.

"People are going hungry, we're aware of that," said Andres Granier, the governor of Tabasco, "but being hungry doesn't justify such behavior."

Smaller looting incidents occurred Friday and police made several arrests, the governor also said.

Felipe Calderon, Mexico's president, said on Friday there were 7,500 military and police staff working on rescue and security operations in Tabasco.

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