A 600-year-old building located in central Seoul which represented the national treasure of South Korea, its symbol, was destroyed in a fire, possibly started by an arsonist on Sunday night.

Citizens remained in shock at the news and many of them rushed to the site to see what was left of the national icon, now in ruins.

Police are conducting an investigation to see whether arson at the Namdaemun gate was the cause of the fire. The gate has survived the 20th century Japanese occupation and the Korean War.

President-elect Lee Myung-Bak, a former city mayor, said: "People must feel hurt by the fire. This is a symbolic place that people want to visit whenever they come to Seoul," AFP reports.

The “Great South Gate,” a building of two stories, caught fire on Sunday evening and by late Sunday it was thought that the fire was under control. Unfortunately the fire ignited again thus destroying the wooden structure.

According to the Yonhap news agency, the fire was reported by a taxi driver who saw a man about 50 years old climbing the stairs just before the fire started.

Professor Lee Su-kyung of Seoul National University of Technology said that the fire could have been controlled from the beginning if the right spot was found by firefighters.

He said: "Someone could have gone inside the structure...I just don't understand."

On Monday a forensic team was at the site searching through debris.

Kim Yong-Su, captain of the Namdaemun police station, said: "Police have not drawn a conclusion yet -- whether there was a short circuit, arson or an accidental fire. Police are still investigating this with all possibilities in mind," Reuters informs.

Police are also verifying the tapes from closed-circuit TV cameras near the gate, but no man was identified entering the building.

The gate was constructed in 1398 and it was rebuilt in 1447. It underwent frequent renovations, the most recent one was from 1961 to 1963. It was called Sungnyemun or "Gate of Exalted Ceremonies", and it was a major tourist attraction.

A restoration was approximated by the Cultural Heritage Administration at about 21 million dollars which will take three years.