No deaths reported, but at least 21 injured in early morning tremblor

At least 21 people were injured and more than 30,000 were evacuated when a magnitude-5.3 earthquake hit a county in Southwest China early on Saturday morning.

The China Earthquakes Network Office said the 13-kilometer-deep epicenter was in Xiluodu township in Yongshan county, Yunnan province.

Two of the injured are in serious condition, according to the county government's information office. Dozens of houses collapsed in the quake, which hit at 6:40 am on Saturday, and two roads were blocked by fallen rocks. One road has since reopened. Communications in the area were not affected.

"We felt the quake strongly, but it did not last long," said a local resident. Some people were woken by the tremblor. They quickly evacuated their homes, but returned a few minutes later.

More than 70 percent of the 600 houses in Fujin village, close to the epicenter, collapsed or were damaged, according to reports on China Central Television.

The authorities have sent 400 tents and quilts for displaced residents in the country, and are ready to dispatch several thousand more.

Yongshan is home to the Xiluodu hydropower project, China's second-largest hydropower station, which is 15 km from the epicenter. There has been speculation that the quake was caused by activity at the power station.

Zhang Jianguo of the Yunnan Disaster Prevention Research Institute denied that there was any evidence to link the quake and the power plant.

The quake did not affect the operation or infrastructure of the hydropower station, China Central Television reported on Saturday evening.

The area has a history of quakes, Zhang said. Quakes caused by reservoir construction usually have quite shallow epicenters, at a depth of around 4 km, while the epicenter of Saturday's quake was 13 km deep. Research into the relationship between earthquakes and hydropower projects remains an important area of research, he added.

Yunnan and Sichuan, its neighboring province, are vulnerable to earthquakes. A number of earthquakes struck Yiliang county and neighboring areas in the provinces of Yunnan and Guizhou in September 2012, killing 81 people.

A magnitude-7.0 earthquake hit Lushan in Sichuan on April 20, 2013, killing at least 196 people. On May 12, 2008, a magnitude-8.0 quake hit Wenchuan, Sichuan, leaving more than 80,000 people dead or missing.