HONG KONG — New economic data from China on Thursday showed that the world’s second-largest economy after the United States expanded at its slowest pace since 2009 during the third quarter of this year — though surprisingly strong data for the month of September also showed that the deceleration may, for now at least, have come to an end.

The Chinese economy has been a major engine of global growth in recent years, as the American and European economies have struggled to overcome the global financial crisis.

The weak global environment has, however, weighed on China’s export sector, slowing China’s once red-hot economy. Government policies aimed at combating inflation and soaring property prices in 2010 and 2011 also have slowed growth.

Beijing released gross domestic product data for the July-September quarter on Thursday that confirmed what has been known for some time: that China’s days of double-digit economic expansion had halted.