MEXICO CITY (Reuters) - Gunmen blocked roads with burning vehicles and exchanged fire with security forces in a central Mexican city on Tuesday, while security officials denied that a wanted gang leader had been captured.

The brazen skirmishes in the city of Celaya in Guanajuato state sparked rumors on social media that security forces had closed in on Jose "El Marro" Yepez, the head of the Santa Rosa de Lima criminal cartel, and possibly arrested him.

The cartel is believed to be behind the massive theft of gasoline from illegal taps on pipelines belonging to national oil company Pemex, a criminal racket that had grown significantly in recent years.

"El Marro" is also suspected of organizing the theft of fuel directly from a nearby Pemex refinery in the city of Salamanca.

His wife was arrested in late January only to be released a few days later after a judge determined there was insufficient evidence against her. Last week, Yepez's father was detained, accused of driving a stolen car.

President Andres Manuel Lopez Obrador aggressively confronted fuel theft early last year, shortly after taking office, ordering the temporary closure of especially vulnerable pipelines which in turn provoked weeks of fuel shortages.

Pemex data shows that the illegal taps fell dramatically last year.

Luis Ernesto Ayala, a senior Guanajuato security official, wrote on Twitter that rumors spread on social media suggesting that an unnamed leader of a criminal group in the state had been arrested were false.

"We continue working in an operation," he added in the post, without providing more details.

Other state and federal security sources also denied that Yepez had been detained.

The violence in Celaya recalled the gunbattles last October in Culiacan, in northwestern Mexico, where hundreds of Sinaloa Cartel fighters temporarily took over the city of about a million people and forced the government to release a son of jailed drug lord Joaquin "El Chapo" Guzman who had been briefly detained.

The chaos marked a major security setback for Lopez Obrador, who has pledged to pacify the country after years of drug-war violence.

(Reporting by Lizbeth Diaz and David Alire Garcia; Editing by Robert Birsel)