Two people remain missing as the search continues for the third day following the collapse of a boiler tower at a decommissioned thermal power plant in the southeastern city of Ulsan.

According to fire authorities on Saturday, an overnight search involving approximately 40 rescue workers, drones, thermal imaging detectors and endoscopy cameras has yielded no results.

Of the seven people who were initially trapped underneath the collapsed structure, three have been confirmed dead, while two others are feared dead.

As rescue workers are having difficulty working in the mangled wreckage, fire authorities are reportedly seeking ways to enhance the efficiency of the search through discussion with rescue safety technicians and other experts.

Rain in the early morning hours made the situation worse.

Authorities are also concerned about two other boiler towers on the verge of collapse on either side of the debris, and have consulted with a representative of the families about blasting and demolishing them sometime next week.

Prime Minister Kim Min-seok visited the site to monitor the ongoing search efforts before visiting the memorial altars of the deceased to console the bereaved families.