A total of 36 local officials in South Korea are under investigation for the tunnel flooding earlier this month that killed 14 people, authorities said.

An inquiry launched two days after the tragedy found that officials had ignored multiple warnings of a flood ahead of the incident.

At least 40 people died in the disaster across the country.

The tunnel, located in city of Cheongju south of Seoul, was flooded with water from a nearby riverbank that had burst from the weekend of torrential rain.

Fifteen vehicles, including a bus, were trapped in the underpass submerged under water - only nine people survived. Authorities had to work for several days to free the vehicles.

Following the incident, police launched an investigation to determine the cause and found that it could have been prevented.

Three calls warning of a possible tunnel flooding were made to the emergency hotlines on the day of the incident, he added.

The public officials have been accused of failing to promptly assess and manage the situation. Two of them were found to have replaced the river embankment - walls meant to prevent flooding - with a weaker version.