Monitoring and prevention efforts will be stepped up as secondary geological events overlapping with the flood season present a tremendous challenge for disaster relief operations in Sichuan province's quake-hit areas, said a senior official of the provincial government on Thursday.

Probe teams have discovered more than 1,900 high-risk spots in Lushan and Baoxing counties, Zhong Mian, executive deputy governor of Sichuan province, said at a news conference in Beijing.

The two counties in Ya'an were the areas most affected by the magnitude-7 earthquake on April 20.