OYO, Nigeria - At least four people were confirmed dead and two others were seriously injured on Thursday when a church building under construction collapsed in Ibadan, capital of southwest Nigeria's Oyo State.

State commissioner for works and housing Yinus Akintunde confirmed the incident to Xinhua, describing it as terrible and disheartening.

Akintunde said those killed in the incident were construction workers at the church building site, and preliminary investigation indicated that contractors of the building project failed to use standard materials for the construction work.

"If the contractor had not compromised quality, this incident would not have happened,"he said, adding that rescue workers quickly arrived at the scene of the incident to provide assistance to the victims.

Governor of the state Abiola Ajumobi and his wife were among early callers and sympathizers at the site.

The governor, while promising that a thorough investigation into the cause of the collapse, said those injured were being treated at an undisclosed hospital in the state.