Beijing, China (CNN) -- An explosion at a coal mine in northeastern China killed at least 11 workers and trapped nearly 128 underground early Saturday, state-run media reported.
The blast happened at about 2:30 a.m. (1830 GMT) at the Heilongjiang Longmei's Xinxing mine, operated by the Hegang company. As of 9:36 a.m., 389 of the 528 workers had reached the surface, state media reported.
A preliminary investigation indicates that the cause was a gas explosion, the Chinese News Service reported.
The blast hit about 10 km from Hegang City.