BEIJING -- Heavy snowfall in northern China is testing the country's disaster preparedness and prompting fresh questions about Beijing's efforts to alter its weather.

A massive blizzard over the past week has dumped some of the heaviest snow in five decades on China's usually arid north, clogging highways and collapsing buildings in seven provinces. The storm, which began Monday, had caused at least $650 million in damage as of Friday afternoon and killed more than 40 people in traffic accidents or building collapses triggered by the snow and ice, the government said.

This week's storm follows an unusually early snowfall that blanketed Beijing on Nov. 1. Government media attributed the intensity of that storm to the Beijing Weather Modification Office, which is responsible for cloud-seeding operations in the capital, whose downtown area is surrounded by farmland. The state-run Xinhua news agency quoted a top official at the office saying it had created 16 million metric tons of additional snow. "We won't miss any opportunity [for] artificial precipitation since Beijing is suffering from the lingering drought," the official, Zhang Qiang, was quoted as saying.

The government's role in that storm angered some people. One blogger on the popular Web site Sohu.com posted a photograph of angry passengers on a grounded flight, and suggested that the weather-modification office should be required to pay compensation for the disruptions the snow caused. "The weather belongs to everyone, not just to the 'Department of Artificial Interference with the Weather,'" he wrote.

At the start of this week's storm -- which dumped varying amounts of snow across the region but totaled well over a foot in some places -- some observers assumed the weather manipulators were at work again. A report in the state-backed China Daily, an English-language newspaper, carried the headline "Weather Is Manipulated Again for Snow," and cited an unnamed official from the weather-modification office saying that it had caused the precipitation, but declining to elaborate.