CHENGDU: China marked the first anniversary of last year's devastating Sichuan earthquake on Tuesday, as the struggle to rebuild vied with new threats from swine flu and economic woes.

The magnitude-7.9 temblor — the deadliest earthquake to hit China in decades — toppled villages and razed portions of Sichuan and two neighboring provinces, leaving nearly 90,000 people dead or missing. Another 5 million were left homeless.

President Hu Jintao was expected to attend commemorations in the quake zone and a grand ceremony was set for the epicenter of the quake in the destroyed town of Beichuan at shortly after 2:00 p.m. (0600 GMT), the time at which the quake struck.

Traffic was heavy outside Beichuan on Tuesday, where refugees from the disaster are living in temporary shelter. Police blocked roads about 5 kilometers (3 miles) from the heart of the old town, leaving hundreds of former residents to stream into the mountains on foot, many heading out before dawn.

In front of the crumbled remains of Beichuan Middle School, mourners piled flowers and were burning candles and incense sticks amid the smoke and crackle of exploding firecrackers.

Amid them, Jin Dalan and her husband Chen Guanghui, 47, burned paper money as an offering to their 17-year-old son who was crushed in the school collapse.

"I'm just trying to talk to him to ask why he doesn't visit me in my dreams. I just want to know that he's OK and that no one is bullying him,' said Jin, 45.

Like many parents of dead students, Chen said he was bitter about the government's treatment of his family, citing claims that school's were inherently unsafe.

"Of course I'm angry. The school was badly built. Nothing else around here collapsed," Chen, 47, said.

Last year's destruction triggered an outpouring of grief around China and united the country in a massive rescue effort boosted by volunteers, private donations, and international aid.

While the government continues to fund reconstruction, the devastation to the local economy and the fallout from the global economic crisis has cast long-term doubts on whether the region will ever fully recover. In the days leading up to the anniversary, the nation struggled with the worldwide outbreak of swine flu, with China's first case officially confirmed in Sichuan's provincial capital of Chengdu on Monday.

The most politically incendiary issue, however, remains the issue of school safety amid allegations that corruption and mismanagement led to shoddy construction.

Parents have tried to sue or petition local and central authorities, but many have been detained or warned against speaking out. Activists and lawyers who have tried to help them have met the same fate and reporters visiting the area have been detained, harassed, and physically threatened.

So volatile is the issue that until last week, the government had refused to release an official tally of students who died, saying the task was complicated and time-consuming. That figure, released in an apparent response to public pressure, showed 5,335 students were killed in the quake_ although parents and activists say the number is too low.

So far, no one has been punished or held responsible over the schools, and officials insist that they have not found evidence so far of shoddy construction — a claim questioned by experts and parents alike.