While not the largest gang in Houston, MS-13 has become a significant player, said Capt. Mike Graham of the Houston police gang division. He said the gang is getting more organized.
"Our biggest challenge is that they are so transient," he said. "They prey on immigrants, but they don't necessarily stay in the immigrant communities. MS-13 is all over the city. If things get hot for them in Houston, they can disappear to North Carolina or D.C."
The FBI now assigns 10 agents to work with Houston police for investigations involving MS-13.
While MS-13 recruits heavily from El Salvador and Honduras and Central American refugees in the U.S., this is no invasion from south of the border. MS-13 is strictly a homegrown gang.
"Only after they were deported did the gang spread to Central America," said UT-Brownsville's Dr. Ritter, who set out to research the gang because she found little information available.
Once back in El Salvador and Honduras, members of MS-13 quickly fought with existing gangs for control, Dr. Ritter said. Both countries got tough, enacting stringent anti-gang laws known as super mano dura, or super hard hand, which provide hard prison time for those simply found to be MS-13 members.
Wherever it spreads, MS-13's business is crime, including drugs, extortion, human smuggling, car theft and contract killings.
"They're very opportunistic and diverse in criminal activities," said Mr. Trucheon of the FBI task force. "In some cities, they specialize in robbery; in others, extortion or crimes of violence. When they move into a community, they'll prey on the lawful and the law-breakers alike."
And intelligence gathered by U.S. and Mexican law enforcement agencies indicates the gang's growing presence in the smuggling operations of Mexican drug cartels.
While the FBI says the evidence is indefinite, other agencies say MS-13 appears to have taken sides with the Sinaloa cartel in its vicious turf war with the Gulf cartel to control narcotics trafficking in Nuevo Laredo.
Like the Zetas, a gang of Mexican ex-military commandos, MS-13 members are believed to serve as cartel enforcers on both sides of the border.
"They've shown themselves willing to hire out to protect drug loads, smuggle aliens and intimidate witnesses. If they can find a way to make a dollar engaging in criminal activity, they'll do it," said Mr. Pena of ICE.
"We have received intel that in a short time, MS-13 has taken control of the rail lines in Southern Mexico used to transport illegal immigrants in from Central America," Mr. Pena said. "They are heavily involved in the human trafficking network, and they collect 'taxes' -- extortion -- from immigrants and the smugglers. MS-13 rapidly becomes a force to be reckoned with wherever they set up."
Many of the gang members apprehended in South Texas by the Border Patrol appear to be new recruits journeying to join cliques in the U.S. or older members traveling on gang business. Some are messengers, a position of trust within the gang's hierarchy.
The biggest border apprehension occurred in February 2005, when a car carrying a load of narcotics was stopped by a Department of Public Safety trooper near Falfurrias in Brooks County. One of the men inside was Ebner Rivera-Paz, a top leader of MS-13.
He had recently escaped from a Honduran prison, where he was being kept for his role in ordering gunmen to open fire on a bus with automatic weapons in Tegucigalpa. Twenty-eight people were killed; the intended target was an enemy of MS-13.
Mr. Rivera-Paz was convicted in federal court for illegal re-entry and deported this year to Honduras. It was his fifth deportation.