At least one person was killed, and dozens were trapped, after a Catholic church collapsed in Nigeria. The incident happened Sunday morning at St. Paul’s Catholic Church in Adagbrasa-Ogolo, located in Delta state in southern Nigeria.

Delta State Governor Ifeanyi Okowa called the incident “sad, unfortunate and regrettable.”

The person killed has been reported in local media as being an 11-year-old boy. At least 15 others were injured, with four people being taken to hospital.

A local police spokesperson said all others have been rescued from the building.

The incident happened as congregants were in the church for prayers before Mass – the priest had not yet arrived to the mission.

“I was inside the church when it happened, it was around 7:30 to 8:00 am. We were having service when it happened … So we just finished sharing the rosary and were singing some hymns when we suddenly started hearing the wall cracking and falling,” parishioner Elohor Amerotoraine told The Nation, a local newspaper.

“At that point everybody started running out to escape the falling walls, [and] before long the entire church had collapsed,” she said.

“My prayers are with the worshipers, affected families, Governor Okowa and the people of Delta State on this morning’s collapse of St. Paul Catholic Church,” said Bukola Saraki, president of Nigeria’s senate, in a message on Twitter.

“We will continue to monitor the situation and provide assistance to see that survivors are rescued and treated,” he said. “Right now, we must all come together as Muslims, Christians, people of faith, and most importantly, Nigerians to provide all necessary relief for the affected families and community.”

“This tragedy affects us all and we join the Catholic community to mourn the deceased,” Saraki stated.

The cause of the collapse has yet to be determined, and Okowa has sent a team to the site to investigate.