Los Ángeles (AP) — Authorities arrested a man who said he left a ruthless street gang in Central America and later won praise for his anti-gang work in Los Angeles last Wednesday, alleging he conspired to kill a rival even.

Alex Sanchez, 37, who heads the local office of the nonprofit Homies Unidos anti-gang group, was taken into custody at his Bellflower home on federal racketeering charges, authorities said.

The indictment names 24 leaders, members and associates of MS-13, part of the Mara Salvatrucha gang affiliated with the Mexican Mafia prison gang.

It alleges crimes that include seven murders, eight conspiracies to commit murder, and gun and narcotics offenses since 1995. Sixteen of those named were already in custody.

The alleged crimes by Sanchez occurred after he returned from El Salvador in 1996 and publicly decried gang life.

The indictment said he went by the nickname Rebelde, or rebel, and was a shot-caller for the Normandie contingent of MS-13. He and three others are accused in the indictment of conspiring to murder a man identified by authorities as Walter Lacinos “for the purpose of maintaining and increasing their position in MS-13.’’

In May 2006, Lacinos was killed in El Salvador.

Mara Salvatrucha was formed in Los Angeles in the mid-1980s by immigrants fleeing the El Salvador civil war. The gang spread as members were deported to their home country and is now a major international criminal enterprise known for callous killings carried out by its members, many of whom are heavily tattooed with shaved heads.

Known as an anti-gang worker, Sanchez has testified as an expert witness in criminal cases, lobbied for better intervention and prevention programs, spoken to youth about the depressing consequences of gang life and been widely quoted in the media.

Luis Romero, director of the Homies Unidos office in El Salvador, said the organization did not accept the allegations against Sanchez.

“We know that Homies Unidos U.S.A. is doing great work in the reinsertion and rehabilitation of young people,’’ Romero said.

Asked what he thought prompted the allegations, he said, “these are the famous smoke screens, things that they use, things that they have not been able to solve and they take action without previously investigating.’’

Sanchez arrived in Los Angeles at age 7 from El Salvador and joined Mara Salvatrucha when he was 14. He was jailed three times for minor offenses and deported to El Salvador in 1994.

He told the AP in a March interview that in his home country he had to live on the streets, fleeing death squads and gangs who threatened to kill him because they believed him a rival.

He returned illegally to Los Angeles in 1995. He was granted political asylum after saying police picked him up because he had testified against officers in the Rampart police corruption scandal.

Several people spoke in his defense, including Tom Hayden, a former student radical and state senator.

In July 2002, Sanchez received political asylum after officials determined his life would be in danger if he returned to El Salvador.

Homies Unidos was founded in 1996 in El Salvador. Sanchez helped establish the Los Angeles office the following year.

Associated Press Writer Marcos Aleman in El Salvador contributed to this story.