A preliminary technical report published by the UN on June 1 said the dam's design did not comply with standard practices and presented structural risks that could cause it to rupture.
EPM said on Thursday that the report was based on a May 18 inspection of the dam in northwestern Colombia.
"They have not seen the progress made since to the main reservoir," newspaper El Tiempo quoted EPM generation chief Luis Javier Vélez as saying.
According to Vélez, reinforcements were made to the dam wall following the UN visit, coinciding with work to raise it to 410m above sea level.
"There are international quality standards ... and we have complied with them. It's an extraordinarily well-constructed dam," Vélez said.
EPM earlier in the week said that leaks identified at the dam were "within the expected ranges" for the current construction stage.
Authorities have maintained flooding alerts for communities along the Cauca river following a series of landslides at the site.
Some 113,000 people have been evacuated from their homes since an initial landslide on April 28 caused the collapse of a tunnel used to regulate the dam's water flow.
Located around 170km northeast of Medellín, Hidroituango is Colombia's largest infrastructure project in investment terms.
The 2.4GW facility, a joint venture between EPM and Antioquia development agency Idea, is expected to supply over 17% of Colombia's electricity when fully operational.
Officials have said the recent chain of events will postpone the start of electricity generation at the plant, which had been slated for December. Last month, experts forecast "brutal" damage to equipment after EPM was forced to release water into the dam's turbine rooms to avoid "catastrophic" flooding.