China’s state news agency says a four-story building under construction in the central part of the country collapsed and killed eight people.

Xinhua News Agency says 100 rescuers were searching for missing workers on Sunday. It was unclear how many people were on the site when the building collapsed Saturday in a suburb of Wuhan city.

Xinhua says 13 people were rescued from the rubble and taken to hospitals. Cranes and other large rescue equipment were having trouble getting to the site because of narrow alleyways in the neighborhood.

Authorities say the construction of the residential building was illegal because it had not been approved by the local government. The cause of the collapse is under investigation.