The statements by Wei Hong, executive vice governor of Sichuan, came after an investigation and appeared to dismiss parents' claims that shoddy construction was to blame for some 7,000 classrooms collapsing — when other nearby buildings stood.
The 7.9-magnitude temblor in May left nearly 90,000 people dead or missing, but the government has never said how many of the casualties were students.
The students' deaths have become a sensitive political issue for the government, with victims' parents staging protests demanding investigations. Many parents have also been subjected to intimidation and financial inducements to silence them.
"The scale of the earthquake was very great and the intensity was very strong, so that was the most important cause of the damage of the school buildings and other facilities," Wei said at a news conference on the sidelines of China's annual legislative session.
Wei said the conclusion was made after an investigation by engineering experts from Tsinghua University and official experts from Sichuan province.
Wei said the quake's destructive force was "one or two degrees" stronger than that which the schoolhouses had been designed to withstand.
It was unclear if the investigation Wei was speaking of was the same as the government's promised probe into possible graft in the construction of schools.
In September, a Chinese government scientist had acknowledged that a rush to build schools in recent years likely led to construction flaws that caused so many of them to collapse — the first official admission that low building standards may have been behind the students' deaths.
Thousands of children are believed to have died in their classrooms during the quake. Wei said the exact number was still being calculated and that the process was "very complicated" because there were various rules that must be followed.
"We need to conduct a series of calculations and checks, especially of the locations and basic information of those missing," Wei said. "Before the exact final death toll has been confirmed, it is very hard to determine the correct number of schoolchildren who died."
While the government has promised an investigation and punishment for those responsible for the poor school construction, there have been no public attempts to hold anyone to account. Marches and sit-ins by grieving parents held within months of the quake were broken up by police, with some parents briefly detained.
In December, the official Xinhua News Agency reported that the Standing Committee of the National People's Congress had passed a law saying that all schools must now be built to higher earthquake standards than other public buildings.