FRANKFURT — When Stefan Jacoby, the chief executive of Volvo, turned up in China on Friday, it was yet another sign of where the action is in the auto industry these days. But some people are starting to wonder whether there is a little too much action.

Mr. Jacoby was in Beijing to announce plans to build a new factory in China, with the goal of selling 200,000 vehicles there by 2015 — an ambitious target, considering that Volvo sold only 374,000 cars worldwide last year.

Volvo’s plans are a logical step for a company, formerly owned by Ford, that is now in Chinese hands. But they are also part of an industrywide rush for a share of the exploding Chinese market. Even General Motors now sells more cars in China than in the United States.

The efforts by Volvo and companies like Daimler of Germany, which said last week that it would build a Mercedes engine plant in China and expand its dealer network there, are raising concerns that car companies may be investing too much in the country, creating an automotive bubble and setting themselves up for a sudden fall.

As auto executives converge on Geneva for the annual auto show in the city, which opens to the news media Tuesday, there are warning signs that China could soon suffer from the same overcapacity that has long afflicted the United States and Europe. Half of the executives surveyed by KPMG, the accounting firm, believe that China will have too many automotive plants within five years, according to a study that KPMG published in January.

“The industry may have to brace itself for some casualties,” KPMG analysts wrote.

For now, though, it is difficult to find an automotive executive who openly expresses anything but optimism about China, or about other emerging markets like Brazil, Russia and India, the rest of the so-called BRIC countries.

China “is a great opportunity in the biggest market of the world,” Mr. Jacoby said, a comment that could have come from many of his peers.

And earlier this month, Dieter Zetsche, Daimler’s chief executive, said at the company’s headquarters in Stuttgart: “We expect to continue posting the highest rates of growth in the BRIC nations, which is why we’ll be paying special attention to those markets in 2011.”

Soaring demand from China played a critical role for Daimler, BMW and Volkswagen during the economic downturn in 2009, partly compensating for plunging sales in Europe and the United States. Now China is helping the German companies achieve record profits and is a major factor in the rebound of the German economy.

VW, the largest European carmaker, said Friday that profit had more than tripled in 2010 to €7.1 billion, or $9.8 billion, from the previous year. The company did not break out revenue by country in the preliminary earnings statement, but China has become Volkswagen’s largest market, and it is a safe bet that sales there were a major factor.

Cars are Germany’s biggest export, and the success of the industry has ramifications around Europe. German growth of 4 percent last year helped to counterbalance the slow growth in countries like Spain and Italy.

Industry analysts agree that a slowdown in the growth rates for Chinese car sales is inevitable, if only because the increases have been so breathtaking. BMW, for example, reported this month that its sales in China had grown 70 percent in January from the same period a year earlier.

“It is very difficult to continually top these very high growth rates,” said Marius Baader, head of forecasting at the German Automotive Industry Association. The organization expects total new car sales in China to grow 11 percent this year to 12.5 million vehicles, after growth of 34 percent in 2010.

But, Mr. Baader said, “11 percent is still pretty good.”

In addition, traffic jams and pollution concerns are prompting Chinese officials to discourage car ownership by limiting new registrations in some cities and removing buyer incentives.

Still, the ratio of people to cars in China is more than 40 to 1, compared with 2 to 1 in Germany, Mr. Baader pointed out. “More and more Chinese have the means to buy cars,” he said. “The potential is huge, even if growth fluctuates from year to year.”

The problem is that all the big car companies are following the same line of reasoning. Though aware that they could be stuck with factories running below capacity, auto executives believe they must invest in China or risk being left behind.

Bain & Co., the consulting firm, has warned that factories in China could be capable of turning out 40 million cars a year by 2015, 35 percent more than the market could absorb, even with exports taken into account. The cost of unused plant capacity could hurt profits and reduce the advantages of producing in China, Bain said in a November report.

Such forecasts do not discourage car companies. “If we do not invest in our plants, then we’ll miss out on sales opportunities, which will be snapped up by our rivals,” Bernd Pichler, managing director for Volkswagen in China, said in the KPMG report. “It’s a risk worth taking.”

Not only is China drawing investment, but the needs of Chinese buyers are beginning to influence global automotive design. BMW, Mercedes and the Audi unit at Volkswagen all make stretched versions of their midsize sedans for the Chinese market. In China, owners of big luxury cars are not the only ones with chauffeurs.

A video of a Volvo showroom in China, displayed on the company’s Web site Friday, is telling. It shows a potential customer scrutinizing a car, then, with the help of a white-gloved sales representative, climbing into the back seat. Volvo, formerly a unit of Ford, was bought last year by Zhejiang Geely of China.

China is also helping to drive the development of electric cars and giving car companies more confidence that they can invest in the new technology and find a market.

With pollution already a grave problem in some cities, carmakers expect the Chinese authorities to put restrictions on gasoline vehicles that would not apply to cars that produced no tailpipe emissions. The European manufacturers also fear that Chinese companies like BYD will get a big lead in battery technology.

The i3 battery-powered car, which BMW plans to start selling in 2013, is aimed partly at wealthier buyers in Chinese megacities. “There will be more regulations that affect mobility,” Ian Robertson, the company’s sales chief, said in Munich this week.

China was also a factor behind the Leaf, the battery-powered car that Nissan is to begin selling this year. “China is a sort of a turbocharger on electric vehicle growth around the world,” said Simon Sproule, a spokesman for Nissan, which is based in Japan and closely allied with Renault in France. China has also become Nissan’s largest market.

Despite the warning signs, there is little indication that automakers plan to scale back their plans for China. Even as growth in China slows, other markets, like Brazil, Russia and India, promise to take up the slack, said Ferdinand Dudenhöffer, a professor at the University of Duisburg-Essen in Duisburg, Germany, who follows the automotive industry.

“India is just as big. There is still Vietnam and other countries,” Mr. Dudenhöffer said. “There is still a lot of potential.”

Somewhat slower growth in China might even be a good thing, he said. “If it doesn’t grow so explosively, that is actually better for the manufacturers,” Mr. Dudenhöffer said. “It’s more stable.”