SAN SALVADOR, El Salvador – Many undocumented immigrants say they're fleeing to the U.S. because of relentless gang violence in their homelands. Last year, nearly 30 percent of unaccompanied minors who entered the U.S. illegally came from El Salvador. The Central American country has one of the world's highest murder rates, and local police told CBS News gang violence is one of its biggest problems.

As darkness fell on El Salvador, CBS News correspondent Omar Villafranca and his team rode along with heavily armed police hunting for members of the notorious MS-13 and Barrio 18 gangs. While driving around, officers immediately stopped their trucks and confronted three men thought to be MS-13. They were pretty sure based on what the men were wearing, especially the Nike shoes, which can be expensive in the country.

Police in El Salvador confronted three men thought to be MS-13. CBS News

The police are out day and night, sweeping neighborhoods paralyzed by gang violence. We were with them as they arrested a man, who they said was a member of MS-13, short for Mara Salvatrucha.

"Are you with Mara?" Villafranca asked.

He told us he is not with MS-13 nor does he have friends in it.

Between 60,000 and around 100,000 Salvadorans are thought to be involved with gangs. The evidence of the gangs are everywhere. We found an area where Barrio 18 put a mural up of everybody who died. It said "In memory of the homies." The mural included their names and gravestones with all their nicknames.

Earlier in the day, police took us to San Martin, a neighborhood they say is controlled by gangs. These houses were once filled with families, but many have now fled, some of them for the U.S. border.

Jose Rubio lived in Los Angeles, but was deported to El Salvador in 1994. The country needs jobs, he said, so people don't have to get involved in gangs. But one woman said the gangs even extort businesses and find ways to force young people to join.

"The gangs grab them," she said, "and they join out of fear they will be killed."

Temporary protected status for immigrants from El Salvador ends September 2019, meaning they may be forced out of the U.S. There's an estimated 200,000 Salvadorans living and working in the U.S. and they send some of their paycheck back home. If that stops, some fear the situation in El Salvador could get even worse.