The Mexican army says it has dealt a significant blow to a powerful drug cartel, with the arrest of one of the cartel leader's security chiefs, as the latest outbreak of violence between warring groups has left at least 13 people dead.

The army said on Monday that special military forces seized computer files and other data when they detained Felipe Cabrera Sarabia, a security chief of Joaquin "El Chapo" Guzman, head of the Sinaloa drug cartel.

General Ricardo Trevillo, the chief army spokesman, offered few details about the hunt for Guzman, one of the country's biggest drug lords.

Trevillo said Cabrera was captured without a shot being fired on Friday in the capital of Sinaloa state, headquarters of the cartel.

Cabrera, nicknamed The Engineer, is said to have been responsible for cartel security in the state of Durango, as well as overseeing drug distribution in parts of Chihuahua. His capture could lead to further arrests.

Bodies found

Separately on Monday, the government announced that troops located 13 dead bodies in an abandoned lorry in eastern Mexico. The corpses suggested "a rivalry between criminal groups", the justice department said in a statement.

The vehicle was found during a routine security patrol near the border between the eastern states of Veracruz, a major
oil-producing region, and Tamaulipas, local media said, citing state officials.

Messages left at the site suggested the dead were killed in a rivalry between criminal gangs, local media reported.

Investigators said the murders are linked to Friday's discovery of 10 bodies in the town of Tampico Alto, in neighbouring Veracruz state, and attacks by gunmen last week on three buses that left 16 people dead.

In September, 35 bodies were dumped along a downtown highway in the Veracruz city of Boca del Rio.

Bloody feud

Two months ago, the government of President Felipe Calderon sent police and army reinforcements into Veracruz after an escalation in killings attributed to the bloody feud between the Zetas, one of Mexico's most violent cartels, and the Sinaloa cartel, which operates in the area.

The move was part of Calderon's national crackdown on drug cartels launched in December 2006. More than 45,000 people have been killed since then in drug-related violence.

Guzman is worth more than $1bn, according to Forbes magazine, which has listed him among the "World's Most Powerful People".

He has a $7m bounty on his head, and thousands of law enforcement agents from the US and other countries are working on capturing him.

His cartel controls cocaine trafficking on the Mexican border with California and has moved eastward to the corridor between the Mexican state of Sonora, which borders Arizona.

Guzman has eluded authorities since his 2001 escape from prison in a laundry lorry.