The latest arrest could lead to US authorities pursuing even bigger targets, said Mike Vigil, former head of worldwide operations for the US Drug Enforcement Agency (DEA).
Mexico's former public security minister, Genaro Garcia Luna, is on trial in NY on separate corruption charges [File: Tomas Bravo/Reuters] Cienfuegos's case is the first time a former defence minister has been arrested and will have far-reaching implications.
Mexico's government militarized the fight against the drug cartels in 2006, since when more than 296,000 people have been murdered, according to the authorities, who say most of the killings are linked to gang violence.
The Mexican investigative magazine Proceso, quoting unnamed sources at the US Department of Justice, reported that the arrest was the result of a long-standing investigation into corruption involving drug traffickers.
Cienfuegos headed the defense ministry under former president Enrique Pena Nieto. Ebrard said Cienfuegos was arrested at L.A. global airport, as he was either arriving or leaving the country.
The high-level arrest comes less than three weeks before the USA presidential election.
As part of his duties, Cienfuegos was the top authority in Mexico's military.
Cienfuegos is accused of alerting cartel leaders to a U.S. law enforcement investigation into its operations and the use of cooperating witnesses and informants, which resulted in the murder of a member of the cartel that leaders incorrectly believed was assisting United States law enforcement authorities.
DEA Los Angeles Division spokesperson Nicole Nishida confirmed the arrest to Reuters but would not provide details of the warrant or the circumstances of Cienfuegos' arrest.
The fall of Cienfuegos marks the first time a former defense minister has been arrested, and will have far reaching implications for Mexico's drug war, which has been led by the armed forces for more than a decade. He is the highest-ranking former Cabinet official arrested since the top Mexican security official Genaro Garcia Luna was taken into custody in Texas in 2019.
Among the thousands of intercepted communications, according to USA prosecutors, were many direct messages between Cienfuegos and a senior leader of the H-2 Cartel, including ones in which the minister discussed his historical assistance to another drug trafficking organization.
The arrest of Cienfuegos is a tough blow for Mexico, where the army and navy are some of the few remaining respected public institutions.
While current President Andrés Manuel López Obrador has vowed to go after corruption and lawbreaking under past administrations, he has also relied more heavily on the army - and charged it with more tasks, ranging from building infrastructure projects to distributing medical supplies - than any other president in recent history. The army under his leadership, however, was accused of carrying out extrajudicial slayings of cartel members and human rights abuses.
The June 2014 massacre involved soldiers who killed 22 suspects at the warehouse in the town of Tlatlaya.