Two workers were killed and five others poisoned Tuesday after an unidentified gas leak at a construction site on a subway line in Guangdong Province, south China, according to the local safety work watchdog.

The accident took place at about 6:15 p.m. when workers were digging through a tunnel 23 meters underground at a section of the No. 6 subway line in Guangzhou, capital of Guangdong.

Investigators from the municipal safety work supervision administration are trying to find out the nature of the gas and what caused the leak.

(Xinhua News Agency April 16, 2008)