DUBAI, UAE (REUTERS) — A fire broke out Monday at an under-construction new terminal at Kuwait International Airport, authorities said, causing damage but no casualties.

Firefighters struggled to control the flames for hours in Kuwait City, Interior Ministry spokesman Tawheed al-Kandari told The Associated Press.

Authorities were still investigating the cause of the blaze, al-Kandari said. The fire caused extensive damage to the building's basement, ground floor, and first floor but no one was hurt, the country's fire services reported.

Photos circulated on social media of dark, billowing smoke behind lines of planes on the runway. Some flights had been delayed on Monday morning though civil aviation authorities said it wasn’t because of the fire.

Kuwait was set to complete construction of the $4.4 billion terminal later this year — a complex architectural canopy of glass and concrete with plans to handle 13 million passengers a year.