GUIYANG - Four people were rescued and casualties remained unknown after a residential building collapsed in Zunyi, Southwest China's Guizhou province early Sunday morning, local publicity department said.

The nine-storey old building on Yan'an Road in the city's Honghuagang District collapsed at around 6 a.m.. Two slightly injured people were sent to hospital, officials said.

Rescue work is underway. The cause of the collapse is still unknown.