A gas explosion ripped through a house where dozens of abducted migrants were being held captive in a city on the Texas border Monday, injuring five people, two of them gravely, Mexican authorities said.

Grupo Coordinacion, a joint governmental security agency in the Gulf Coast state of Tamaulipas, said in a statement that the afternoon blast blew out the windows and doors of the home in Reynosa, which is across from McAllen, Texas.

Three of the five were hospitalized, and all were from Guatemala. The most seriously injured were said to be in delicate condition after suffering burns over much of their bodies.

Authorities were trying to locate an unknown number of migrants who may have been injured but ran away after the blast, which was blamed on an accumulation of natural gas.

Investigators determined the house was being used by a criminal gang to hold captive at least 60 migrants of different nationalities who were trying to get to the United States. The migrants told police they were abducted a week ago.

Migrants traveling through Mexico are frequently preyed on by organized crime groups who extort ransom payments from them or their families.

Reynosa is considered a stronghold of the Gulf cartel, which controls the drug trade in much of the Tamaulipas-Texas border region.