South Korea's landmark ancient architecture of Sungnyemun Gate, which is located in central Seoul and has a 610-year history, collapsed early Monday after catching fire.

South Korea's "No. 1 national treasure" Namdaemun blazes as firefighters try to extinguish it in Seoul, South Korea, Feb. 11, 2008. (Xinhua/AFP Photo)

The wooden structure of the gate caught fire at about 8:50 p.m. Sunday (1150 GMT Sunday) and collapsed at around 1 a.m. Monday (1600 GMT Sunday), local government said.

The Sungnyemun Gate was the southern gate of the walls that surrounded Seoul during the Joseon Dynasty (1392-1910). The construction of the gate began in 1395 and was finished in 1398 during the reign of King Taejo, who founded the Joseon Dynasty.

It is the oldest wooden structure in Seoul and was designated the No. 1 National Treasure in 1962.

The cause of the fire was under investigation. Local police said it might be an arson as a taxi driver who reported the fire told police that he saw a man in his 50s went into the gate shortly before the blaze started.

The collapse of the gate is expected to trigger severe criticism against the Cultural Heritage Administration, which is in charge of maintaining cultural and historical artifacts, including national treasures, local media said.

Firefighters try to extinguish a fire at Namdaemun, a historic gate which was given the status of National Treasure No. 1, as the gate is collapsing in central Seoul February 11, 2008. The fire broke out on Sunday at Namdaemun, the oldest wooden structure in Seoul, and the cause of the fire has yet to be determined. (Xinhua/Reuters Photo)

Firefighters try to extinguish a fire at Namdaemun, a historic gate which was given the status of National Treasure No. 1, as the gate is collapsing in central Seoul February 11, 2008. The fire broke out on Sunday at Namdaemun, the oldest wooden structure in Seoul, and the cause of the fire has yet to be determined. (Xinhua/Reuters Photo)

South Korea's "No. 1 national treasure" Namdaemun blazes as firefighters try to extinguish it in Seoul, South Korea, Feb. 11, 2008. (Xinhua/AFP Photo)

(Xinhua News Agency February 11, 2008)