An injured young boy is transferred by a helicopter to Zhaotong City from Longjing Village of Longtoushan Town of Ludian County, southwest China's Yunnan Province, Aug. 6, 2014. Death toll from a 6.5-magnitude earthquake that hit Yunnan on Sunday rose to 589. (Xinhua/Hu Chao)

BEIJING, Aug. 6 -- China's earthquake authority has warned of possible strong aftershocks following the 6.5-magnitude earthquake that rattled southwest China's Yunnan Province on Sunday.

The quake zone is likely to face aftershocks at 5 to 6 magnitude in the next few days, said Pan Huaiwen, director of the China Earthquake Networks Center (CENC), during an online interview at www.china.com.cn on Wednesday.

"It does not mean that such aftershocks are due to happen but we can not rule out the possibility," Pan said.

He suggested rescuers and locals in the quake-hit areas remain vigilant and prepare for aftershocks.

The CENC is also closely monitoring the local situation, he said.

The death toll of the quake reached 589 on Wednesday.

Pan attributed the high casualty rate to the poor condition of local buildings and the harsh mountainous environment.

He ruled out a connection between the quake and the development of reservoirs and hydropower plants in Yunnan in recent years.

A strong earthquake like this one is always linked to crustal movements and local geological structures, according to the CENC chief.

Commenting on China's earthquake early warning system, Pan said the country has started the research but there is still much work to be done.

The country has improved the speed of detecting a quake and sending out the data but much more effort is needed to optimize responses to early warnings, he noted.