Latvian rescuers end search after supermarket collapse, final death toll at 54

Policemen stand near a collapsed Maxima supermarket in Riga, Latvia, Sunday, Nov. 24, 2013. A massive third section of the roof at the supermarket where scores of people were killed fell as emergency workers searched nearby rubble for more victims. Investigators are looking at faulty construction or work on the roof's grass and gravel covered surface as the potential cause of the initial collapse in the crowded supermarket on Thursday. (AP Photo/Mindaugas Kulbis) (The Associated Press)

Policemans stands near a collapsed Maxima supermarket in Riga, Latvia, Sunday, Nov. 24, 2013. A massive third section of the roof at the supermarket where scores of people were killed fell as emergency workers searched nearby rubble for more victims. Investigators are looking at faulty construction or work on the roof's grass and gravel covered surface as the potential cause of the initial collapse in the crowded supermarket on Thursday. (AP Photo/Mindaugas Kulbis) (The Associated Press)

RIGA, Latvia – Latvia's rescue service says it has finished searching the site of a collapsed supermarket in which 54 people died, including three firefighters, and at least 40 were injured.

The four-day operation was interrupted on Saturday when a large portion of the roof caved in, but no one was injured.

Prime Minister Valdis Dombrovskis on Monday called the supermarket collapse a "serious crime" and said it is not a case where there can be no guilty party.

Latvian officials say 40 people are participating in the investigation, which will likely take several weeks. Possible explanations for the disaster include a flawed design, substandard construction materials, and corruption.