Prosecutors in Mexico said Thursday they have arrested two more men in the March 3 kidnapping of four Americans, two of whom were killed.

The Gulf drug cartel turned over five men to police soon after the abduction in the border city of Matamoros, and prosecutors said the two newly arrested suspects also appeared to be members of the same cartel.

The two were arrested during raids in the northern border state of Tamaulipas on Sunday and flown to Mexico City on a military plane. It was not immediately clear why the arrests were not announced at the time.

Federal prosecutors did not provide the full names of the suspects, but the details and first names match two men listed on a federal database as being arrested in Tamaulipas that day. Those names — Axel Alfredo Cárdenas and Alan Alexis Cárdenas — suggest they are related to Osiel Cárdenas Guillen, the Gulf cartel leader captured in 2003.

Prosecutors confirmed the two were sons of Osiel Cardenas' nephew, José Alfredo Cárdenas Martínez, who was arrested in 2022. They also said the pair assumed leadership roles in the cartel following their father's arrest.

The two allegedly headed up the gangs of cartel gunmen known as the Scorpions and the Cyclones. They were caught in an early morning raid in which police found six guns and over a thousand doses of "synthetic drugs," a term used in Mexico to refer to either methamphetamines or fentanyl.

The statement did not specify the charges the men would face, but it said they had been engaged in drug and migrant smuggling, kidnappings and extortion in the Matamoros area.

In March, less than a week after the abductions, a letter claiming to be from the Gulf cartel's Scorpions faction condemned the violence and said the gang had turned over to authorities its own members who were responsible. A Mexican woman also died in the March 3 shootings.

"We have decided to turn over those who were directly involved and responsible in the events, who at all times acted under their own decision-making and lack of discipline," the letter reads, adding that those individuals had gone against the cartel's rules, which include "respecting the life and well-being of the innocent."

Five men were found tied up inside one of the vehicles that authorities had been searching for, along with the letter.

The four Americans crossed into Matamoros from Texas so that one of them could have cosmetic surgery. Around midday, they were fired on in downtown Matamoros and then loaded into a pickup truck.

Americans Zindell Brown and Shaeed Woodard died in the attack; Eric Williams and Latavia McGee survived. Most of them had grown up together in the small town of Lake City, South Carolina.

A Mexican woman, Areli Pablo Servando, 33, was also killed, apparently by a stray bullet.