As of 22:00 p.m. Monday, nine workers were still missing the two workers njured were out of danger after a blast took place at an explosive plant Saturday in east China's Shandong Province, according to local police sources.

The blast occurred at a privately-owned explosive plant in the city of Zhaoyuan.

Altogether 31 workers were working at the plant when the blast happened, and 20 were killed on the spot.

The two injured workers were immediately sent to the Zhaoyuan People's Hospital, where they received treatment from a medical team headed by the hospital's deputy director Xu Xuebin.

Xu said though the two workers were out of danger, they still needed intensive care in the hospital.

Rescuers are sparing no efforts to search the missing, and investigation into the cause of the blast is also underway.