An underpass has been flooded by water overflowing from the Miho River in Cheongju, North Chungcheong Province, rescue workers said Saturday.

The number of people trapped in the tunnel is unclear. As of 9 p.m. police said 11 people have been reported missing, and confirmed 15 vehicles including a public bus to be trapped in the underpass.

Gungpyeong 2 Underpass in Osong-eup was submerged around 8:40 a.m. Saturday after the banks of the river collapsed and water flooded into the four-lane tunnel.

The rescuers from Korea Fire Agency have so far found one body at the scene, as well as nine survivors who clung onto guardrails around the tunnel.

Based on the CCTV footage, the police confirmed that a total of 15 vehicles, including one public bus, two trucks and 12 cars, were trapped in the tunnel.

A survivor from the bus told local media that there were at least eight others who were in the vehicle at the time of the flooding.

The authorities dispatched 279 personnel to the scene with four rubber boats, but water kept flooding into the 430-meter-long tunnel. The current and the mud prevented divers from entering the flooded area.

Cheongju City have started work to drain the tunnel and shore up the collapsed bank, but it was still uncertain how long it would take to complete the rescue as of Saturday 8 p.m.