An office building in downtown Shanghai caught fire on Sunday morning, but no casualties were reported so far.

The city's fire brigade said the fire took place at around 10:30 a.m. at the four-storey Qianchen office building on East Yan'an Road in Waitan.

The fire was ignited on the first floor of the building, said the fire brigade, and then spread to the upper floors, filling the building with dense smoke.

Few people were inside the building when it caught fire. The firefighters rescued one person who was trapped in the fire and no one has been reported injured or dead in the fire.

The fire was quenched about one hour later and investigation into the cause is already underway.