(CNN) -- Latvian Prime Minister Valdis Dombrovskis is resigning in the wake of a deadly supermarket roof collapse, his spokesman said Wednesday.
Dombrovskis is "taking political responsibility for the tragedy," spokesman Martin Punke told CNN.
The roof collapse last Thursday in the Zolitude neighborhood of the capital, Riga, left more than 50 people dead -- the deadliest incident in Latvia since the country became independent in 1991.
Dombrovskis, who has been prime minister since March 2009, is expected to address the nation in a news conference Wednesday afternoon.
His decision to step down came after a meeting with the president, according to Latvia's national news agency, LETA.
The news agency quotes Dombrovskis as thanking Latvians for their support during the economic and financial crisis and apologizing "for all that we have failed to achieve."
A total of 54 people, including three firefighters, died in the collapse and several dozen were injured, LETA said.
In the wake of the tragedy, President Andris Berzins told Latvian television that "nature could not be blamed" and that those involved needed to think about what they had done, so that action could be taken.
"This incident is basically the mass murder of a large number of defenseless civilians. We must act accordingly,'' Berzins said.
The cause of the disaster is still under investigation. However, Riga Mayor Nils Usakovs told CNN last week that authorities think building materials stored on the roof caused it to collapse.