BEIJING, June 14 (Xinhua) -- China's investment in property development expanded 10.2 percent year on year in the first five months of this year, the National Bureau of Statistics (NBS) said Thursday. The growth was slightly slower than 10.3 percent in the January-April period. Investment in real estate development stood at 4.1 trillion yuan (about 650 billion U.S. dollars) in the first five months, according to the NBS. Residential real estate investment reached 2.9 trillion yuan, up 14.2 percent year on year, with the growth flat with that of the first four months. Investment grew fastest in the northeastern region -- 19.9 percent -- up 9.2 percentage points from the January-April period. Real estate developers were built about 6.8 billion square meters of housing in the first five months, up 2 percent year on year. Commercial housing sales measured by floor area rose 2.9 percent year on year, up 1.6 percentage points compared with the first four months. Sales in value climbed 11.8 percent, up 2.8 percentage points. At the end of May, about 560 million square meters of housing was unsold in China, down 6.8 million square meters from a month earlier.