TIJUANA – In the first such measure in Mexico, a new electronic system has been implemented that blocks transmissions from cell phones and radios coming from inside the state prison here.

The goal is to put an end to the extortions that prisoners are able to carry out against families in the community, said the state's Secretary for Public Safety, Daniel de la Rosa.

Inmates at the La Mesa prison made continuous phone calls asking people to buy a phone card in exchange for a chance to win a prize or threatened to hurt a relative if they did not deposit money into an account.

The authorities even conducted informational campaigns to warn the population about these frauds, acknowledging that prisoners in state custody were behind some of these calls.

The prison in Tijuana will be the first penitentiary in Mexico to use the blocking technology, made in Israel, which cost the state around $1.6 million, De la Rosa said.

This prison, also known as "El Pueblito," has been severely overcrowded for years, which has led to conflicts among prisoners, murders and riots. Currently, there are more than 7,000 men and women housed there.

In September of 2008 guards beat a 19-year-old inmate to death, which sparked a series of riots that left 24 people dead and more than 50 injured.

De la Rosa said the new system will not only block all cellular transmissions from inside the cells but from all administrative offices, as well. In fact, he said, the system cannot be manipulated by the prison staff.

Inmates will only be able to make calls using regular telephones during limited days and times.

The new system, however, will not interfere with the quality of phone and radio service in the surrounding area, he said. The plan is to roll it out to prisons statewide, he added.

"This way we can slam the door on any type of call that can be used to carry out a crime," he said, "as was the case with these extortions."

Omar.Millan@sandiegored.com