Mexican authorities have arrested a suspected paymaster of the Zetas drug gang linked to the murder of a U.S. customs official in Mexico that raised tensions in the two nations' fight against organized crime.

In a statement on Wednesday, the Federal Police said they took 41-year-old Mario "El Mayito" Jimenez into custody over the killing of U.S. Immigration and Customs Enforcement (ICE) agent Jaime Zapata on February 15.

The United States responded with outrage to the murder of Zapata, who was traveling unarmed when suspected drug gang members shot him and his partner on a busy highway in the state of San Luis Potosi. The other ICE agent survived.

The shooting was one of the worst attacks on U.S. personnel in Mexico, causing strains in the two countries' joint efforts to battle the cartels and prompting some U.S. lawmakers to press for U.S. agents to be able to carry arms in Mexico.

The police allege Jimenez manages the payroll for Zetas' hitmen in San Luis Potosi, in addition to collecting revenues from drug sales and purchasing real estate and equipment for the cartel's operations.

Formed by renegade special forces soldiers, the Zetas became the armed wing of the Gulf Cartel before splitting from their masters last year in a violent struggle to secure control of lucrative smuggling routes in northern Mexico.

They are feared as one of the most brutal cartels in Mexico, where more than 35,000 people have been killed in the army-led crackdown on drug gangs launched by President Felipe Calderon after he took office in late 2006.

Washington has backed Calderon's crackdown, but cooperation has been hampered by mistrust between the two neighbors' intelligence agencies and finger-pointing over who is to blame for the failure to curb the rising tide of violence.

Late last month, the Mexican Navy arrested the alleged head of the Zetas in San Luis Potosi, Sergio "El Toto" Mora, in connection with the attack on the ICE agents.