MONTERREY, Mexico (AP) -- Some Mexican priests, tired of Mass being interrupted by ringing cell phones, are using counterintelligence technology made in Israel to silence the devices.

In four Monterrey churches, cell phone blockers the size of a hand-held radio have been tucked among the paintings of the Madonna and clay statues of saints to bring peace back to Mass.

"There are still many people who don't understand that being at Mass is sharing a moment with God," said Juan Jose Martinez, a priest and spokesman for the Monterrey Archdiocese. "Sadly, we had no other choice but to use these little gadgets."

The churches began using the cell phone blockers, made by the Tel Aviv-based Netline Communications Technologies, after Rodrigo de la Mora, an insurance salesman, imported them as a personal favor for a priest.

The wall-mounted jammers were developed by former Israeli military and defense officers to avert eavesdropping on security-sensitive conversations and to prevent bombs from being detonated by a mobile phone.

The devices, purchased for about $2,000 each, can be turned on by remote control. They emit low-level radio frequencies that thwart cell phone signals within a 100-foot radius.

Users get a "no service" or "signal not available" message on their cell phones and incoming calls do not get through.

In Mexico, mobile phones have outnumbered fixed lines, and one in every four Mexicans now has a cell phone, according to Mexico's Federal Telecommunications Commission.

But as mobile phones are becoming part of daily life, so are their nuisances, including users chattering away in movie theaters, restaurants and churches.

The frequent use of mobile phones at Sacred Heart church in downtown Monterrey, a baroque temple favored for weddings by the rich and famous, prompted church officials to acquire the blockers two years ago.

For months, the devices went unnoticed until reporters covering the weddings noticed their cell phones never worked at that church. Since they wrote about the jammers, priests from around Mexico have been calling to find out how to get them, said Bulmaro Carranza, a parish clerk at Sacred Heart.

Now priests in Mexico City and Guadalajara are also requesting the jammers, De la Mora said.

Whether the use of cell phone blockers in Catholic churches has become common is unclear. The Vatican doesn't track how many churches around the world are using the devices but it does acknowledge cell phone use during Mass has become a headache.

Netline did not return a call asking for comment, but company officials have said they are selling thousands of devices a year via the Internet and expanding their business all over the world.

At Sacred Heart, a device at the entrance to the church and another by the altar are turned on right before every Mass. Still, priests remind parishioners to turn off their phones before beginning the services, hoping good cell phone etiquette will eventually catch on.

"Whenever there was a wedding, cell phones would ring every five minutes," Carranza said. "It was a real problem because there were times when even the groom would forget to turn his cell phone off."

The Rosario, San Juan Bosco and Our Lady Queen of the Angels churches have also followed suit. There are more than 200 churches in Monterrey, many of them with few resources, and priests still hope they can avoid the jammers and trust that politeness will prevail.

The four churches with the devices are frequented by mainly wealthier parishioners, Martinez said.

"For a lot of them, the cell phone is a necessity. But that shouldn't prevent them from having good manners and remembering that one must respect sacred places," Martinez said.

Blocking cell phone signals in the United States is illegal, but Mexico does not yet have a regulation against it, according to an official with Mexico's Federal Telecommunications Commission who spoke on condition of anonymity.

Margarita Escobedo, a Catholic who goes to church at least twice a week and volunteers at the San Genaro church, says she would welcome the jammers at her church, where cell phones are becoming an irritating nuisance.

"Those who bring cell phones to church are not committed to God," Escobedo said. "It's very distracting to be praying and suddenly hear birds chirping or techno music."

Copyright 2004 The Associated Press.