A mudslide has struck a village in Mexico's southern Chiapas state, leaving at least 16 people missing, feared dead, officials say.
Helicopter crews are trying to evacuate local residents
The slip followed heavy rain which has caused severe flooding in Chiapas and in the neighbouring state of Tabasco.
Foreign aid is beginning to arrive in the region but big difficulties remain in distributing the aid.
Water levels remain high and thousands of people are still waiting for food and other supplies.
The floods that hit last week are some of the worst in Mexico's history.
As many as half a million people have seen their homes damaged or destroyed, and at least 20,000 people remain trapped in their homes.
The Mexican military has rescued almost 40,000 people in the two states.
Rescue teams were despatched to the community of San Juan Grijalva, where heavy rainfalls caused a hillside to collapse into a river.
Local media reports said the landslide buried many houses and as many as 30 people could be missing.
Some residents are thought to have fled into the hills to escape the advancing wall of mud and debris.
"This village practically disappeared," the Associated Press quoted Chiapas governor Juan Sabines as saying at the scene.
International help for the flood-stricken communities has begun to arrive, reports quoted Mexico's foreign affairs ministry as saying.
Financial help, emergency personnel and supplies from several countries are being added to hundreds of tons of aid provided by ordinary Mexicans.
Tabasco capital Villahermosa is among the places worst affected
Donations have been pledged by countries including Ireland ($1.4m), the US ($300,000) and Germany ($250,000).
Peru is said to be sending a planeload of supplies, Britain 10 experts and inflatable boats, and Cuba 50 doctors.
Hundreds of tons of emergency supplies have been dispatched by Mexicans, following an appeal for solidarity from President Felipe Calderon last week.
Flood waters which reached 2m (6ft 7in) at the peak of the flooding are now reported to have begun receding, but conditions remain difficult, reports the BBC's Andy Gallacher in southern Mexico.
Isolated communities have yet to receive any fresh water or medical supplies, our correspondent says, and tens of thousands of people are housed in evacuation centres, where conditions are deteriorating.
In the hard-hit state capital, Villahermosa, fights broke out over sparse supplies of aid.
About 50 people were reportedly arrested over isolated looting incidents during the weekend.
The state governor, Andres Granier, closed some central commercial streets of Villahermosa to prevent more looting before the waters abate.
In one piece of good news, our correspondent reports, forecasters say no rain is predicted for the next few days.