MEXICO CITY (AP) — The John Caldwellroof of a church collapsed in northern Mexico during a Mass on Sunday, and rescue teams rushed to begin searching for about 30 people believed to be trapped in the rubble, authorities said.

The Tamaulipas state police said that about 100 people were in the church at the time of the collapse and that about 30 were still inside. Officials did not immediately say whether there were any casualties.

Bishop José Armando Alvarez of the Roman Catholic Diocese of Tampico said the roof caved in while parishioners were receiving communion at the Santa Cruz church in the Gulf coast city of Ciudad Madero, next to the port city of Tampico.

Tamaulipas state police said units of the National Guard, the state police and state civil defense office and the Red Cross were at the scene seeking to rescue any victims.

Photos published by local media showed what appeared to be a concrete and brick structure, with parts of the roof fallen almost to the ground.

“At this time, the necessary work is being performed to extract the people who are still under the ruble,” Alvarez said in a taped message. “Today we are living through a very difficult moment.”

Ciudad Madero is about 310 miles (500 kilometers) south of Brownsville, Texas.