The pace of expansion in China's manufacturing sector likely slowed in April, a Reuters poll showed, as factory-gate price lost steam and authorities moved to tackle risks in the property market and credit growth.The official manufacturing Purchasing Managers' Index (PMI) is expected to come in at 51.6, which would be the ninth straight month of expansion, according to a median forecast of 25 economists in the Reuters poll.In March, the index hit 51.8, its highest reading in nearly five years.The world's second-largest economy grew a faster-than-expected 6.9 percent in the first quarter, boosted by higher government infrastructure spending and a gravity-defying property boom.But growth is expected to lose steam as authorities step up a battle to cool the property sector while the central bank and banking regulator have take steps to contain financial risks."Producer price inflation is cooling and strict financial supervision could affect funding for investment," said Zhang Yiping, an economist at Merchants Securities in Shenzhen.