KUNMING -- A 12-km-long tunnel on the Kunming-Vientiane Railway to link China with Laos was drilled through on Monday morning.

The Shitouzhai tunnel, located in Yutang town, Mojiang county of Southwest China's Yunnan province, is one of the 93 tunnels along the 508 km Yuxi-Mohan section of the Kunming-Vientiane Railway. So far, 70 tunnels have been drilled through, according to the China Railway Kunming Group Co., Ltd.

Large air conditioners and ice makers have been used to help construction workers cope with the high temperature during drilling, according to Wang Li, a project manager.

The Yuxi-Mohan section in China is scheduled to be opened simultaneously with the Boten-Vientiane section in Laos by the end of 2021.