Police investigating a deadly fire at the soundproof tunnel on the second Gyeongin Expressway in Gwacheon, Gyeonggi Province, which killed five people on Dec. 29 last year, have raided a road management company.

Gyeonggi Nambu Provincial Police Agency said Friday that it raided the offices of the 2nd Seoul-Incheon Linking Highway Co. as well as the Seoul office of a company entrusted with road management work on Thursday.

The search and seizure operation, which involved 22 investigators, lasted about five hours from 3:30 p.m. on Thursday. Police secured information including safety manuals, status information of fire extinguishing facilities and records of disaster prevention facilities. Based on the obtained information, police will further investigate whether the company’s follow-up actions after the fire were appropriate.

Police said Tuesday they booked two officials from the 2nd Seoul-Incheon Linking Highway Co. on charges of negligence resulting in death. Police assessed that they had not taken proper follow-up measures after the fire.

Among the emergency blocking facilities installed at both ends of the tunnel, only the one installed in the direction of Anyang to Seongnam operated normally. The facility in the opposite direction did not work.

As all five victims were found in vehicles on the lane driving toward Anyang, critics have pointed out that the malfunctioning blocking facilities were at fault in the casualties.

In addition, the issue of the combustibility of plastic materials used is continuously being raised. The Ministry of Land, Infrastructure and Transport held an expert meeting Wednesday and discussed measures to improve the fire prevention system regarding soundproofing facilities installed on roads, and ordered the replacement in soundproof tunnels and soundproof walls of polymethyl methacrylate for nonflammable materials.

The fire, which led to five deaths and 41 injured, started from a truck passing through a soundproof tunnel on the Second Gyeongin Expressway near North Uiwang Interchange, at 1:49 p.m. on Dec. 29. The fire spread rapidly in the tunnel made of combustible plastic material, burning a 600-meter section of the 830-meter tunnel.