The Mexican military killed 11 suspected Gulf cartel members and captured 36 more in a major crackdown that began last week, officials said on Monday.
Among those arrested was Gabriela Gomez Robles, known as "La Gaby," who is believed to be the finance chief of the drug-trafficking group, said military spokesman Admiral Jose Luis Vergara.
Also detained was Ricardo Salazar Pequeno, an alleged Gulf cartel boss, Vergara added.
The operation was launched October 5 in Tamaulipas, one of the most violent areas in Mexico. Officials also seized four tons of drugs, numerous weapons and one anti-aircraft missile.
Tamaulipas is the scene of a bloody turf battle between the Gulf cartel and former allies known as the Zetas, led by former elite military officials.
Mexican authorities used Black Hawk helicopters loaned by the United States under the Merida Initiative, during the operation.
Almost 45,000 people have been killed across Mexico since the federal government in 2006 launched a crackdown against drug cartels, according to official data and media tallies.