MEXICO CITY — The Mexican authorities on Sunday detained several suspects implicated in the massacre of nine members of a Mormon sect in northern Mexico in early November, according to the office of the nation’s attorney general.

The detentions came during a joint operation by members of the Mexican armed forces and intelligence agents and followed the detention last month of another suspect living in Mexico City, the attorney general’s office said in a statement, providing no further information about the suspects’ identities, their connection to the murders or the circumstances of their arrests.

In his first year in office, President Andrés Manuel López Obrador has struggled to articulate a coherent crime-fighting strategy, and to curb spiraling violence and the immense power of organized crime groups. The failure was highlighted by this harrowing incident, which rose above the usual drumbeat of news about bloodshed in Mexico, in part because the victims were women and children and dual American and Mexican citizens.

Mr. López Obrador took office last year vowing to remove the military from the streets in the fight against drug trafficking organizations and end his predecessors’ war on drugs. Instead, he promised, he would address the roots of crime by tackling poverty through social development programs and investment — a strategy he refers to as “hugs, not bullets.”