CIUDAD MADERO, Mexico - The roof of a church collapsed in northern Mexico during a Mass on Sunday, killing at least nine people and injuring around 50, authorities said as searchers probed in the wreckage late into the night looking for survivors and other victims.

Approximately 30 parishioners were believed to have been trapped in the rubble when the roof caved in, officials said. Searchers crawled under the roof slabs and officials brought in dogs to help search for possible survivors.

The Tamaulipas state police said about 100 people were in the church at the time of the collapse.

The state security spokesman's office said late Sunday that nine people had been confirmed dead from the collapse, which it described as likely being caused by "a structural failure."

Tamaulipas state police said units of the National Guard, the state police and state civil defense office and the Red Cross were involved in the operation.

The Mexican Council of Bishops issued a statement saying that "we join in prayer at the tragic loss of life and those injured."

Bishop Jose 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.

The diocese later posted a list of about 50 people who had been hospitalized as a result of the accident. They included a 4-month-old baby, three 5-year-olds and two 9-year-olds. There was no immediate information on their conditions.

The number of young victims - police officers said three of the dead were children - may have been due to the fact that baptisms were to take place at the church.

"We lament the painful loss of people who were there celebrating the baptism of their children," Alvarez wrote.

At the same time, there were signs of hope.

"From underneath the rubble, thanks to Divine Providence and the work of the rescue teams, people have been pulled out alive!" Alvarez's diocese wrote in a statement posted on it social media accounts. "Let's keep praying!"

He also called on anyone who had wood to donate to bring it to the church, apparently to shore up the roof while rescue teams crawled inside.

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. Security camera footage from about a block away showed the unusual, gabled roof simply collapsed downward.

Walls did not appear to have been blown outward, nor was there any indication of an explosion, or anything other than simple structural failure.

The roof appeared to be made of relatively thin poured concrete, and photos distributed by state authorities showed the roof slab resting on the top of pews in some parts of the church. That left open the possibility there were air spaces for any survivors.

"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."

Video distributed by the state civil defense office showed the outer edges of the roof propped up by short wooden blocks.

It also showed initial efforts to lift off parts of the collapsed roof closer to the ground, in the center of the church, with a crane. But the office said the efforts to lift roof sections were abandoned because of the danger that a chunk of the now-crumbling slab might fall back and endanger any survivors.

The video described how officials had reverted to manual rescue efforts, apparently sending rescuers under the slab with wood props or hydraulic jacks to reach those trapped underneath. Specially trained dogs also were sent into the rubble to detect survivors.

The civil defense office said the dogs did not initially appear to detect signs of survivors, so an older method was implemented that had been used in past earthquakes: sending rescue teams into the rubble to shout and listen for signs of any response.

Building collapses are common in Mexico during earthquakes, but the National Seismological Service did not report any seismic activity strong enough to cause such damage at the time of the collapse. Nor was there any immediate indication of an explosion.

Ciudad Madero is about 500 kilometers south of Brownsville, Texas. Tamaulipas is known for drug cartel violence, but Ciudad Madero is in the southern part of the state near neighboring Veracruz state and has been less touched by the violence.