The civil defense office of Veracruz state said five more people were injured in the Rio Oro canyon, near the Gulf of Mexico.
The accident occurred Sunday, and the office said searches continued Monday with police, volunteer rescue groups and firefighters participating.
The office did not release the names or nationalities of the victims, but such expeditions are popular among young Mexican tourists.
Canyoning involves hiking, climbing, rappelling and swimming through river canyons. The Rio Oro canyon includes waterfalls and relatively narrow rock passages.