AN explosion in Laiwu City, Shandong Province registered as a 3.5-magnitude earthquake at 7:55pm yesterday, Xinhuanet.com reported today.

The Seismological Bureau of Shandong Province recorded the tremor and sent officials to investigate. Officials reckoned the center of the blast was in Yanzhuang Town but failed to pinpoint it.

Laiwu City has several coal mines and the wave formation recorded by the bureau indicated the tremor was caused by artificial explosion possibly in a mine. The bureau and the city government are still searching for the cause.

Residents 15 kilometers north of Yanzhuang Town felt the quake. People in Laiwu gathered in the square or streets, not daring to return home last night. A government official told Xinhuanet.com many residents had called to ask whether there had been an earthquake.

The bureau and the government has reassured residents through television and radio announcements and advised them to return home. Residents in Laiwu are reportedly calm.