Pope Francis is "deeply saddened" to hear about the 11 people killed and 60 injured by a natural gas explosion at an apartment building in Argentina's third largest city.

"The Holy Father, deeply saddened to hear the painful news of the violent explosion that happened in Rosario … prays for the repose of the deceased, and raises fervent prayers to the Lord that he grant comfort to those affected by misfortune, inspiring in all feelings of Christian hope and fraternal solidarity," reads an Aug. 7 telegram sent to Archbishop José Luis Mollaghan of Rosario.

The message, which was sent in the Pope's name by Vatican Secretary of State Cardinal Tarcisio Bertone was read in public during a Mass and procession for Tuesday's feast of Saint Gaetano, Argentina's most popular saint.

The cause of the Tuesday morning blast is under investigation, but according to interviews the local media conducted with residents, the massive explosion was happened when a repairman was trying to replace a gas valve.

Residents of the nine-story, three-tower complex had been complaining of leaks and low gas pressure for weeks and a July 26 repair by the company Litoral Gas SA did not resolve the issues.

"So the residents' committee consulted with gas repairmen, and they said the valve had to be changed. That was the work they were doing," resident Marcos Morales explained to La Capital newspaper.

Judge Juan Carlos Curto, who is investigating the incident, emphasized to reporters that the blast "isn't something that just happened yesterday, but rather it had been coming for days with different jobs by Litoral Gas and by repairmen, not just the detained one, and this resulted in yesterday's repair job that was directly linked to the explosion."

The strength of the morning blast severely damaged two buildings and collapsed a third. It also caused authorities to close a large part of downtown Rosario, which is home to 1.2 million people.

Search and rescue efforts have been going on since the explosion, with most of the work being done by hand and lightweight equipment, since several of the buildings affected by the blast seem near collapse.

The latest count of victims lists 11 fatalities, 60 wounded and 11 missing, according to the Associated Press.

Pope Francis finished his message by extending the victims and their families the consolation of his apostolic blessing.