The State Administration of Work Safety Tuesday said the fireworks plant in northeast China that exploded on Monday leaving at least 20 dead, did not have a production permit.

Local work safety department confiscated the plant's production permit in June this year and asked it to improve its safety work, said a statement from the administration.

Preliminary investigations show the plant was engaged in illegal production, said the statement.

The accident in Heilongjiang Province left 20 dead, four missing and another 153 injured, local authorities said Tuesday.

The explosion occurred at 9:45 a.m. Monday at the factory in the Wumahe District of Yichun City.