The authorities confirmed the deaths were caused by the floods, taking the disaster's toll to 10.
A week of flooding has driven about half a million people from their homes and the authorities are trying to deliver much-needed food, water and shelter to at least 20,000 stranded people.
A mudslide in the southern state of Chiapas, waterlogged after days of heavy rain, buried part of a community of about 150 families.
The number of deaths was unclear because officials were waiting for rescuers to report back from the disaster scene.
Dozens have been reported missing in the landslide.
Al Jazeera's Franc Contrears reporting from Tabasco's capital, Villahermosa, said there was concern about a possible outbreak of dengue and cholera.
He said authorities were expecting the situation to worsen after more rain was forecast for Wednesday.
Contrears said an estimated 900,000 homes were destroyed and many among the evacuees were worried about the flood damage and looting.
Camped on rooftops
In the worst-hit state of Tabasco, where 80 per cent of the territory was submerged, many remained camped out on the rooftops or upper floors of their furnished homes to guard their possessions from looters.
Most of Mexico's south remained
However, some were forced to give up their attempts at saving their goods.
"I would prefer to be in my house instead of a shelter, but we ran out of everything", said Patricio Bernal, 53.
She was evacuated by boat along with his wife from their home in the state capital, Villahermosa.
Rescuers are now said to be undertaking "selective evacuations", primarily of sick people, and delivering supplies to isolated communities surrounded by water.
Visiting Tabasco, Felipe Calderon, the Mexican president, said: "We are seeing one of the worst natural catastrophes in the history of the country.
"Not only because of the size of the area affected, but because of the number of people affected."
The government has said about half a million people have been affected by severed utilities and transportation links since rivers first burst their banks on October 28.
Four bridges and 290km of roads have been washed out in the neighbouring state of Chiapas.
The US has pledged $300,000 in emergency aid to the worst-hit states of Tabasco and Chiapas.