The disaster, which killed at least 25 people, has shown a light on corruption said to be rife in the Russian capital's construction business.
President Vladimir Putin offered condolences to the victims and said "the culprits must be punished." Deputy Prime Minister Vladimir Yakovlev called for tougher punishment for those convicted of negligence in construction. The maximum sentence now is five years in prison.
Rescuers continued the search for bodies amid the glass and debris at the site, where passers-by laid flowers and small icons in the snow. Moscow's city prosecutor Vladimir Yudin said four or five people remained unaccounted for, a figure that was lowered after some reported missing were found.
In their criminal investigation into who is to blame for the disaster, prosecutors collected debris from the wreckage and amassed documents from firms involved in building the water park, one of several flashy facilities opened in recent years on Moscow's outskirts.
The water park included a sauna, suntanning facilities, a large pool, an artificial river and a long water slide. The collapse of the vast glass roof left a gaping hole of 5,400 square yards and torn insulation panels hanging off the walls of the cavernous building.
Investigators' "main task is to look at the foundation, the analysis of the ground conditions, and the design decisions taken ... the quality of metal and concrete used," said Nikolai Koshman, the chief of the government agency in charge of construction.
Experts said corrosion and insufficient ventilation could have weakened the concrete-and-glass structure and made it more vulnerable. Also, chlorine vapors and the wide difference between temperatures indoors and outdoors would have speeded up the development of metal fatigue, Valery Goreglyad, a specialist on water parks, was quoted as telling the Izvestia newspaper.
But Russian media and other experts blamed widespread neglect of safety norms and official corruption.
"On practically any construction site in the capital a system of mass corruption is flourishing — from receiving licenses to the substitution of one brand of concrete for another cheaper brand or simply for sand," Alexei Klimenko, an adviser to the Moscow mayor, was quoted as telling the Kommersant newspaper.
"The system has collapsed," echoed the daily Vremya Novostei, which alleged that the accident had resulted from cronyism, graft and thefts in the city's construction business.
The licenses of the Turkish company that built the park, Kocak Insaat, and the Russian architects who designed it, Sergei Kiselyov and Partners, were suspended pending the investigation — though the architects said Monday another firm designed the building's cupola, which collapsed.
Turkish newspapers quoted Ismail Kocak, the Turkish company's owner, as denying responsibility and allegations that low-quality materials were used in constructing the building, which opened in 2002 and was built in 18 months.
By Vladimir Isachenkov