Pena took a grim tour of La Pintada, a small town in Guerrero inundated by torrential rains and mud flows last week.
"To date there is virtually no hope that we can find someone alive. The amount of land that buried more than 40 houses in this small community leaves us hardly any hope to find people alive," Pena said, according to a translated dispatch from El Universal.
Troops were in the areas where Hurricane Ingrid and the powerful Tropical Storm Manuel swept through. They helped clear debris and look for missing people.
The death toll was pegged at around 100 Sunday.
Unsettled weather continued Sunday, keeping the threat of new flooding alive.