China's National Bureau of Statistics (NBS) on Tuesday attributed a discrepancy between industrial output and power generation growth in May to industrial restructuring and the use of energy-efficient products.

Industrial output expanded 8.9 percent in May from a year earlier, while power generation fell 2.7 percent.

Although the two figures usually track one another, they've begun to diverge as many industries undergo structural change and improve their energy efficiency, the NBS said in an online statement.

Such discrepancies had occurred before, usually when the economy hit a turning point, said the statement.

The statement attributed the faster-than-expected industrial output growth to a rebound in the growth rate of heavy industry, accelerating growth in almost three-quarters of all 39 industrial categories, higher growth rates in 20 of the 31 provincial regions and output gains in quake-hit Sichuan Province.