A 22-year-old male medical student went missing during a heavy downpour in the southwestern city of Iksan, North Jeolla Province Wednesday, Jeonbuk Provincial Police said Thursday.

A search operation was underway but bore no fruit as of press time.

Authorities said emergency number 112 received a report at around 11 a.m. on Wednesday that the missing student had gone outside their guesthouse in Iksan, early in the morning and had not been heard from since. There were reportedly 24 medical students on a membership training field trip. The student left the guesthouse reportedly at 4 a.m. saying he was going outside to smoke.

When he left the lodging facility at around 4 a.m., a heavy rain warning was issued in the area, according to officials. At the time, torrential rains of 60 to 80 millimeters per hour were pouring down, submerging roads and disrupting drainage systems.

The record heavy rain that battered South Korea's southern regions Tuesday evening and Wednesday morning had left at least six dead and two missing as of Thursday at 6 a.m., according to the Central Disaster and Safety Countermeasure Headquarters.

Upon receiving the report, the police and fire authorities immediately dispatched 25 rescuers and conducted search operations in the area but failed to locate the missing student as of press time. They have expanded the search for the student by deploying 100 more personnel to the site, drones and specially trained dogs to assist in the rescue on Thursday.

Police said determining the missing student's whereabouts is difficult as the lodging is located on the city's outskirts, and there are few surveillance cameras in the area.

Officials said they plan to mobilize more personnel and riot police units to join the search operation.

Meanwhile, the Interior Ministry deactivated the disaster control office's level 2 emergency operations as of Wednesday at 8 p.m., as the heavy rain advisory had been lifted.