The tunnel of an airport under construction in Kunming, capital of southwest China's Yunnan Province, collapsed Tuesday evening, injuring 11 people, including three severely, local authorities reported Wednesday.

The accident occurred at around 7:10 p.m. Tuesday when 19 people were working at the scene of an uncompleted tunnel, according to Kunming Municipal Information Office.

The injured were rushed to hospital immediately.

Eight slightly-injured people suffering bruises were discharged from the hospital. The other three severely injured were still receiving treatment in the hospital but were in stable condition.

Rescuers had searched the scene three times and confirmed that there were no other casualties.

A further probe into the cause is under way.