Four workers were killed and 19 others injured Monday in a fire at a construction site for a national art museum in central Seoul, fire authorities said. The blaze broke out at around 11:20 a.m. in the third basement floor of one of the buildings under construction to house a Seoul branch of the National Museum of Contemporary Art, the fire officials said. The fire that ripped through the site left four dead, they said. One was critically injured and 18 others were being treated for inhaling inhalation from the fire, they added in remarks relayed by the South Korean Yonhap news agency. The fire sent plumes of black smoke rising above Gyeongbok Palace, which is situated right next to the museum, but did not spread to the palace, one of the country's top tourist attractions. The incident caused tourists and residents in nearby neighborhoods to be evacuated. Firefighters extinguished the fire in about one hour and 20 minutes, but said they could not promptly put out the fire due to so many insulators lying around. "The fire is suspected to have broken out when the workers were working with urethane, combustible material used for insulation work," a fire official said. Up to 160 firefighters and 30 fire engines were deployed to tackle the blaze and the additional rescue force was sent to search for possible survivors and wounded. Police and fire authorities said that they will determine the exact cause through questioning of the workers and further look into the possibility of any violation of security regulations. The culture ministry said it was not sure whether the fire will cause a delay in the construction, set to be completed in 2013. "We'll conduct a safety check of the construction site after the accident comes under control to judge whether any delay is needed or not," Na Jong-min, a spokesman for the Ministry of Culture, Sports and Tourism, told reporters. The National Museum of Contemporary Art headquartered in Gwacheon in the southern suburb of Seoul has a small branch museum inside Seoul's Deoksu Palace and plans to add two more, including the main Seoul branch under construction, within the next two years.