Aerial photo taken on May 29, 2019 shows the scenery of Nanhu Lake scenic area in Tangshan, north China's Hebei Province. (Photos: Xinhua)

A worker is seen at a lithium battery manufacturing plant for automotive use in Tangshan, north China's Hebei Province, April 11, 2019.

Aerial photo taken on May 29, 2019 shows the view of Tangshan City, north China's Hebei Province.

Aerial photo taken on Oct. 6, 2017 shows the Yuedao island scenic area of Tangshan international tourism island in Tangshan, north China's Hebei Province.

Photo taken on May 31, 2019 shows the production line of bullet train of CRRC Tangshan Co. Ltd. in Tangshan City, north China's Hebei Province.

Photo taken on May 31, 2019 shows the sewage treatment area of HBIS Group Tangsteel Company in Tangshan, north China's Hebei Province.

A worker of HBIS Group Tangsteel Company patrols at the steel coil storage area in Tangshan, north China's Hebei Province, May 31, 2019.

A technician checks fire-fighting robots at a robot company in Tangshan City, north China's Hebei Province, June 11, 2019.

Aerial photo taken on June 11, 2019 shows ships docking at ore wharf of Caofeidian Port in Tangshan, north China's Hebei Province.

Aerial photo taken on June 11, 2019 shows people visiting Kailuan national mining park in Tangshan, north China's Hebei Province.