The inquiry will focus on whether building regulations were enforced and whether officials had planned adequately for natural disasters.
At least 290 people are now known to have died in Saturday's disaster and more than 300 are still missing.
About 2,700 residents are living in shelters.
Some areas remain without water and electricity, and police reinforcements have been sent in to deter looters.
"This is not about punishment it's about prevention," said national comptroller Edgardo Maya, who ordered the inquiry.
"What good does it do to punish people now, after (so many) deaths?"
A separate investigation is focusing on the regional governor, the town's mayor and their predecessors, Colombian media reported on Wednesday.
Meanwhile, rescue teams continue the grim search for victims buried under piles of debris.
The landslide followed a night of heavy rain which caused the Mocoa River and three tributaries to burst their banks.
The flood sent a torrent of mud and rocks pouring into the town, sweeping away entire neighbourhoods.
The government has faced criticism that it did not act quickly enough - a claim disputed by President Juan Manuel Santos.
He said new systems had been put in place following deadly floods in 2010 and that rescue agencies were co-ordinating their efforts just hours after the disaster.
BBC News |
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