The authorities have voiced concerns that the hurricane-hit towns are more populated than the Yucatan Peninsula that was ravaged by the hurricane earlier in the week, Contreras said.
He added that some cities have as many as 300,000 residents while many villages are scattered in the mountainous areas where coffee crops grow.
"What keeps us in a state of alert is the enormous amount of water," Fidel Herrera, the governor of Veracruz, told Televisa television.
Category 1 – Winds 119-153kph
Minor coastal flooding and structural damage
Category 2 – Winds 154-177kph
Damage to roofs, mobile homes and shanty houses. Some trees uprooted. Small boats may break moorings
Category 3 – Winds 178-209kph
Damage to buildings, mobile homes destroyed. Severe flooding near to coast
Category 4 – Winds 210-249kph
Major structural damage, roofs destroyed. Storm surge around 5m requiring widespread evacuation of coastal areas
Category 5 – Winds 249kph or higher
Serious damage to all but strongest buildings. Severe flooding far inland, all trees blown down. Storm surge up to 6m above normal
Mexico suspended its offshore oil production and shut down its only nuclear power plant as tens of thousands headed for higher ground.
Dean had struck land on Wednesday as a category two storm after regaining some of the force it unleashed on the Yucatan.
Its first strike there on Tuesday was the third most intense landfall ever for an Atlantic hurricane.
Dean was little more than a shadow of the monster storm that roared onto Mexico's Caribbean coast on Tuesday, but the authorities are worried that as many as 3.5 million residents could be at risk from swelling rivers and landslides.
At least 10,000 others were evacuated from Tuxpan, a few kilometres up the coast from Dean's most destructive winds.
Meanwhile officials said there were still no reports in Mexico of deaths directly caused by Dean, which killed 13 people as it tore through the Caribbean.
The biggest threat to life may be mudslides in the mountains of Veracruz and that authorities were worried that mudslides could be deadly for villagers in the area, Contreras said.
Dean first made landfall on Tuesday as a rare Category 5 hurricane, capable of catastrophic damage, but the storm's top winds were relatively narrow and appeared to hit just one town as it travelled west across the Yucatan.
The cruise-ship port of Majahual, with only a handful of residents, was in the hurricane's path and all the people had been evacuated although the town was badly damaged.