Authorities have launched a joint inspection into a deadly fire at a hotel construction site in the southeastern port city of Busan that killed six workers and injured 27 others.

The on-site inspection started at 10:30 a.m. Sunday and involved a joint team comprising experts from the police, fire authorities and the National Forensic Service.

Police are working to determine the original point and exact cause of the fire after securing witness statements that the fire started at a plumbing maintenance room on the first floor near the swimming pool.

The Busan Regional Employment and Labor Office is investigating some 40 contractors involved in the construction for potential violation of the Serious Accidents Punishment Act.

The police plan to conduct an autopsy on six victims of the fire on Monday to determine the exact cause of death. 

The fire broke out at the Banyan Tree Hotel construction site in Gijang County, Busan, around 10:50 a.m. Friday.