Monterrey, Mexico, Feb 2 (EFE).- Two American missionaries were strangled to death with wire in Santiago, a rural city in the northern Mexican state of Nuevo Leon, police said.

The bodies of Wanda Casias, 67, and John Frank Casias, 76, who were from Colorado and had lived in Mexico for about 25 years, were found by their son at a ranch located about 37 kilometers (23 miles) from Monterrey, the capital of Nuevo Leon, a State Investigations Agency, or AEI, spokesman told Efe.

The woman's body was found in the kitchen and the man's body was in the yard, the AEI spokesman said.

The victims were beaten and then strangled with wire, which was found around their necks.

The bodies of the couple, who were missionaries with the First Independent Fundamentalist Baptist Church, were found on Tuesday afternoon.

Investigators are trying to determine whether robbery was the motive for the killings, the AEI spokesman said.

Electric appliances, a pick-up truck and other property were missing from the house.

Santiago, a popular tourist destination, has been rocked by drug-related violence in recent years.

Santiago Mayor Edelmiro Cavazos was kidnapped and murdered on Aug. 15, 2010, by gunmen working for the Los Zetas drug cartel, which was trying to take control of the town.

Santiago police officers guarded and assisted the hired guns who killed the mayor.

The mayor was the victim of what Mexican officials call a "levanton," a kidnapping with no ransom demands usually staged by drug cartel enforcers to obtain information via torture or to kill the victim for having betrayed the criminal organization