The cause behind the collision between two heavy vehicles in Gwacheon, which took place around 1.50pm local time and sparked a huge fire on the stretch, is not immediately known. The details of the contents of the cargo are also not immediately known.
Three of the injured are in a serious condition while the other 34 have light injuries, the country’s national fire agency said.
“Three have suffered burns on facial areas while the rest are being treated for smoke inhalation,” an official from the Gwacheon fire department said.
The collision occurred inside a noise-barrier tunnel on the highway.
Preliminary visuals of the accident showed a swathe of the raised tunnel set ablaze from the fire’s impact. Visuals on TV also showed plumes of smoke billowing from the tunnel.
The firefighters have brought the blaze under control, officials said, adding that the crew members are carrying out a search and rescue operation inside the tunnel in case of additional casualties.
Around 50 fire engines and equipment, as well as about 140 firefighters, were dispatched to the site of the accident. It is also not clear where the five dead have been reported from in the incident, the public affairs office said.
Officials also said around 20 more people were under treatment after inhaling toxic gas.
Seoul’s interior minister Lee Sang-min asked authorities to deploy “maximum resources” to save lives, reported South Korean Yonhap news agency.
“I urge the authorities to put out the best efforts to save the lives of those who have not escaped,” he said.
The fire accident comes just months after South Korea saw its deadliest Hallowean tragedy in late October which killed at least 150 people in a stampede.