Thousands of people were plucked from rooftops in southern Mexico on Sunday as water receded after flooding that left 800,000 homeless in Tabasco state, authorities said.

The army evacuated 5,000 people in a four-hour operation with 14 helicopters, police official Daniel Montiel said, as more food and bottled water was trucked in to crammed shelters that were struggling to provide enough meals and dry beds. Army officials estimated another 80,000 people were still trapped in flooded homes, local media reported. Aerial images showed the area resembling a huge lake with just the tops of roofs poking through. More than 30,000 people have been evacuated by the army and navy teams in helicopters or boats, civil protection officials said. People are hunting for relatives and fighying over dwindling food and drinking water supplies.

The floods, some of the worst the low-lying region has seen in 50 years, were triggered when heavy rain this week caused the Grijalva River to swell and burst through sandbags in the city.