China has begun expanding the world's deepest underground lab in southwest Sichuan Province, where scientists are conducting experiments on mysterious "dark matter". The second-phase of construction of the Jinping Underground Laboratory, located at 2,400 metres under the surface of Jinping Hydropower Station, was launched yesterday by Tsinghua University and Yalong River Hydropower Development Company, the university told state-run Xinhua.

The construction, scheduled to be completed by the end of 2015, will increase the lab's space to 120,000 cubic metres, allowing more experiments to be carried out simultaneously, the university said.