The roof collapse happened Thursday in the Latvian capital of Riga, with a final section falling Saturday evening, Euronews.com reported.
At least 54 people died in the collapse, but officials said the death toll may raise as seven people are still missing.
Speaking with public LTV broadcaster, Berzins said Latvia would hold three days of national mourning for the disaster, the BBC reported.
"These three days of mourning are very necessary to go from the mindset of helplessness to rethinking what each of us has done so that we can act in practical manner, because this is an event where we must clearly say that this is a large scale murder of many defenseless people and act accordingly," Berzins said.
Berzins called for an investigation to determine the cause of the collapse to be conducted at "maximum speed."
"While not undermining the professionalism of our builders, I believe that we should call upon international expertise which is in no way connected with our construction business," Berzins said. "We cannot call it a natural accident, because nature wasn't involved. The evening was calm and silent with a little fog. This is our own made disaster."