MOSCOW — Rescuers searched Monday for more victims of the weekend roof collapse at a Moscow water park and President Vladimir Putin pledged to punish those responsible if faulty construction or maintenance is found to be the cause.

Twenty-five people were confirmed dead in the collapse Saturday night. Moscow Mayor Yuri Luzhkov said Monday that the death toll could rise by up to 13.

Luzhkov, who visited the ruins of the Transvaal Park outside Moscow, said there was no hope of finding anyone alive in the rubble. The victims included seven children, prosecutors said.

Luzhkov and other officials have said there was no evidence of a terrorist act in the collapse of the concrete-and-glass structure on Moscow's southwestern outskirts and pointed to possible construction flaws or poor maintenance.

Prosecutors have opened a criminal investigation into negligence leading to deaths and started collecting debris for analysis.

Putin offered his condolences to the victims, promising that the accident would be thoroughly investigated. "The culprits must be punished," he said.

Russian media said that widespread neglect of safety norms and official corruption might have contributed to the disaster.

"In Russia, they try to finish and sell buildings as quickly as possible, and they don't care about what will happen next," the daily Gazeta quoted construction expert Viktor Ovsyanikov as saying.

Experts said that an excessive buildup of snow on the roof and insufficient ventilation could have weakened the structure and made it more vulnerable to the stark difference between the warmth indoors and the cold outside.

Nikolai Koshman, the chief of the government agency in charge of construction, told reporters Monday that an official panel would report a preliminary conclusion by the end of the week.

"Their 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," Koshman said.

He said the authorities were checking several facilities of similar design, including Moscow's Luzhniki sports arena.

Koshman's agency already has suspended the licenses of Kocak Insaat, the Turkish company that built the park, and the Russian architectural firm that designed it.

Turkish newspapers quoted Ismail Kocak, the company's owner, as saying the roof was designed to withstand 1.5 metres of snow but there was twice as much when it collapsed. He denied allegations that low-quality materials were used in construction.

City authorities said they would pay the equivalent of $4,590 Cdn to relatives of each victim.