The volcano briefly erupted Saturday, prompting authorities to issue evacuation orders after local vulcanologists warned more eruptions were likely, Colombia Reports reported Monday.
"They have not evacuated all who should have been evacuated. How many were supposed to be evacuated?" Santos said. "Four thousand people were supposed to be evacuated and 1,710 were evacuated. What does this say us? That we lack education and a little more collaboration and social discipline. Here we have to improve."
Santos said communication problems between national government and local government agencies present a problem, Colombia Reports said.
"Here we need … a parallel information channel," Santos said.
The 17,457-foot Nevado del Ruiz volcano is one of the deadliest volcanoes in Colombia. Following an eruption in 1985, an avalanche erased the town of Armero, killing 25,000.