Municipal officials from all over China have been flocking to Guangzhou to ask for details. Xi’an, the metropolis of northwestern China, has already announced this month that it will limit car registrations, although it has not settled on the details.

The Chinese auto industry has grown tenfold in the last decade to become the world’s largest, looking like a formidable challenger to Detroit. But now, the Chinese industry is starting to look more like Detroit in its dark days in the 1980s.

Inventories of unsold cars are soaring at dealerships across the nation, and the Chinese industry’s problems show every sign of growing worse, not better. So many auto factories have opened in China in the last two years that the industry is operating at only about 65 percent of capacity — far below the 80 percent usually needed for profitability.

Yet so many new factories are being built that, according to the Chinese government’s National Development and Reform Commission, the country’s auto manufacturing capacity is on track to increase again in the next three years by an amount equal to all the auto factories in Japan, or nearly all the auto factories in the United States.

“I worry that we’re going down the same road the U.S. went down, and it takes quite some time to fix that,” said Geoff Broderick, the general manager of Asian operations at J. D. Power & Associates, the global consulting firm.

Automakers in China have reported that the number of cars they sold at wholesale to dealers rose by nearly 600,000 units, or 9 percent, in the first half of this year compared to the same period last year.

Yet dealerships’ inventories of new cars rose 900,000 units, to 2.2 million, from the end of December to the end of June. While part of the increase is seasonal, auto analysts say that the data shows that retail sales are flat at best and most likely declining — a sharp reversal for an industry accustomed to double-digit annual growth.