China's work safety watchdog Wednesday announced that 27 people have been punished over an explosion that killed four people last month at a tank storage area owned by PetroChina in Northeast China's Liaoning Province.

The State Administration of Work Safety said the blast on June 2 in Dalian Petrochemical Company in the coastal city of Dalian caused a direct economic loss of 6.97 million yuan ($1.13 million).

According to the investigation by the local government, the blast was caused by nonstandard gas cutting on a tank full of inflammable gas and reasons behind it include the chaotic management of fire-related operations and a lack of effective supervision.

Three people were transferred to the judicial authorities for criminal prosecution.