RIGA - The death toll from the roof collapse at a supermarket in the Latvian capital Riga on Thursday has risen to 52, media reported on Saturday.

The latest body was found at 6:00 am (0400 GMT) and the rescue operation is still underway, according to media reports.

Rescue workers told Xinhua that they were still hoping to find more survivors trapped inside the wreckage.

The supermarket, built in 2011, belongs to the Lithuanian-owned Maxima chain, the second largest retailer in the country.

The reason for the collapse is currently unknown, but reports have said a garden with trees and plants was being built on the store's sizeable roof, which might have violated construction regulations and triggered the collapse.

Latvia on Saturday began three days of mourning over the tragedy, which is the worst accident in the Baltic country in over 20 years.

Latvian President Andris Berzins told local media on Saturday that the accident should be viewed as a murder case and he called for investigation as fast as possible.