Those skeptical about the data point, in part, to the underlying numbers.

For example, electricity consumption, long a barometer of economic health and of the veracity of economic statistics, was nearly unchanged last year instead of rising in line with growth in China’s gross domestic product. Some have cited the lack of correlation as a sign of possible fudging in the country’s economic statistics, while optimists have said that the figures may show how China is shifting away from energy-intensive manufacturing.

State news media reported last month that several officials in northeastern China had admitted to inflating investment figures and other data in previous years. Such moves, the reports indicated, helped explain steep drops in reported data from the region last year.

Still, the bureau has consistently and repeatedly defended its statistics, contending that critics do not adequately understand the data or the Chinese economy. And the market impact of the investigation could be limited by the fact that many were already wondering about China’s data.

“The international credibility of China’s G.D.P. figures is anyway very low, so this probably is not a severe blow,” said Diana Choyleva, the chief economist and head of research at Lombard Street Research, an economic analysis group in London. Lombard estimates that China’s gross domestic product grew 3.2 percent last year, not the 6.9 percent that the National Bureau of Statistics claims.

The reliability of China’s economic data goes to the heart of the market’s concerns.

At the official rate, China grew last year at the slowest pace in 25 years. The government is trying to manage a slowdown without letting the pain create social unrest.

That can make it hard to discern what’s really happening in the economy. Among other problems, it has a glut of old-line factories that make products like steel, glass and cement. That industrial overcapacity stems from years of debt-financed investment in industries that now show little sign that they can repay those loans.