Seven people fell ill after suffering from what appeared to be carbon monoxide poisoning at a construction site in Paju, Gyeonggi Province on Thursday.

According to local fire authorities, the workers fell ill while curing concrete at the apartment construction site in the Dongpae area. 

Authorities said two were seriously injured, while five others sustained minor injuries. The authorities initially announced that four were seriously wounded, but revised its findings after the status for two of them improved.   

Fire authorities are checking the apartment building under construction to find any other casualties.