Chinese manufacturing activity strengthened in September to its highest level in 17 months, the government said Tuesday, providing further evidence of a rebound in the world\'s second-biggest economy. The official purchasing managers\' index (PMI) crept up to 51.1 last month from 51.0 in August, the National Bureau of Statistics (NBS) said on its website. The index -- which measures manufacturing activity in Chinese factories and workshops -- is a widely observed monitor of the country\'s economic health. A reading above 50 indicates expansion while anything below signals contraction. The September PMI is the highest since a reading of 53.3 in April 2012, and comes alongside other recent numbers that suggest the Chinese economy is picking up steam. Another key indicator -- the PMI as measured by the British banking giant HSBC -- rose to 50.2 last month, up from 50.1 in August and well up from an 11-month low of 47.7 in July. China\'s economy expanded 7.7 percent in 2012, its slowest pace in 13 years. Year-on-year growth continued at 7.7 percent in the first three months of this year before dropping to 7.5 percent in April-June. But recent data, including strong exports and industrial output, have pointed to renewed strength.