CIUDAD VICTORIA, Mexico — An alleged top boss of the Gulf drug cartel was captured by Mexican marines Monday in the northern border state of Tamaulipas, which for years has been terrorized by gangland violence.

A statement from the Mexican navy said the suspect it identified only as Jose Alfredo, with no last name, was arrested in the city of Matamoros, which is across from Brownsville, Texas.

"Presumably he was the leader of a criminal organization in the region," the statement said.

A state government official with knowledge of the case confirmed that the detained man was Jose Alfredo Cardenas, alias "the Accountant" and "Mr. Polite."

He is nephew to the brothers and former Gulf cartel leaders Osiel and Antonio Cardenas; the former is in a U.S. prison, while the latter was killed by Mexican security forces in 2010.

The official, who was not authorized to discuss the case publicly and spoke on condition of anonymity, said no shots were fired in the pre-dawn raid. Authorities seized two military-grade weapons, ammunition, a vehicle and some cocaine and marijuana.

Tamaulipas, a key corridor for smuggling drugs and migrants to the United States, has long been plagued by cartel violence. The state is one of five in Mexico for which the U.S. State Department issued its highest warning level — "Do Not Travel" — under new guidelines last month.

Amid frequently shifting criminal alliances and loyalties in the state, since 2014 the Gulf and Zetas cartels have been pitted against a breakaway faction of the Zetas that calls itself the Cartel of the Northeast.

The faction is largely led by relatives of Miguel Angel Trevino Morales, alias "Z 40," a Zeta kingpin who was captured in 2013.

The dispute has rocked Tamaulipas as well as nearby Nuevo Leon, Zacatecas, San Luis Potosi and other states where the Zetas have a presence and the Northeast cartel is now fighting them.

The war has claimed the lives of gangsters, police and civilians. Tamaulipas recorded 805 murders across the state last year, up sharply from 595 in 2016, according to federal government statistics.