At least three people died and more than 180,000 others were affected by the torrential rains that hit southern Mexico's Isthmus of Tehuantepec over the weekend, officials in Oaxaca state said.

Two people died in Salina Cruz, a city southeast of Oaxaca city, the state capital, and one person died in San Jose Chiltepec, north of the capital, Gov. Gabino Cue said.

Gabriel Lopez Estudillo, 82, and his daughter, Sandra Luz Lopez Luca, 34, died when a mudslide buried their house in the Isthmus of Tehuantepec region.

A woman died when she was swept away early Sunday by a river in San Jose Chiltepec, a city in the Papaloapan Basin region near the border with Veracruz state.

Emergency management officials plan to survey families affected by the rains to determine their needs once the clean-up is completed, Cue said.

An emergency declaration was requested on Sunday for 42 of Oaxaca's 570 municipalities so federal reconstruction assistance can be obtained, state government secretary-general Irma Piñeyro Arias said.

The torrential rains "have caused damage to dwellings and the main access routes to areas affected by the storm," Piñeyro Arias said.

Army troops activated an emergency plan to assist residents of cities in the Isthmus of Tehuantepec, the area most affected by the heavy rains from a tropical wave.

Health Secretariat teams have fanned out across the region, providing medical care and disease prevention services to residents affected by flooding in Salina Cruz, Tehuantepec and neighboring cities, such as San Mateo del Mar, San Pedro Huamelula and Santiago Astata, among others, officials said.

Oaxaca Infrastructure Secretariat and water commission personnel are moving heavy equipment and trucks into affected areas as part of the clean-up operation.

A mudslide blocked the Istmo-Huatulco highway in the city of Salina Cruz, making it difficult to access the area.

Several rivers and streams have overflowed their banks in the Isthmus of Tehuantepec region, with water levels reaching 1.5 meters (nearly five feet) in some places.

The torrential rains that hit the region over the weekend were produced by tropical wave No. 9, which affected southern, southeastern and central Mexico.