A top Mexican Cabinet official resigned Tuesday after someone threatened to ruin his career by leaking secretly recorded conversations.

Transportation and Communications Secretary Luis Tellez didn't say why he was stepping down. But he quit two weeks after Mexican media reported the contents of a conversation recorded in 2006 in which Tellez alleged that former President Carlos Salinas stole from a secret government fund.

Tellez, whose responsibilities included airline and telecommunications regulation, told federal officials he had received a letter threatening to reveal other recordings and urging him to "resign before your life is converted into a scandal," his office said.

Tellez now regrets making the accusations because he has no evidence of corruption during the 1988-1994 Salinas presidency, his office said. The statement did not say whether Tellez knows the source of the threatening letter.

President Felipe Calderon on Tuesday named Juan Molinar, the director of Mexico's Social Security Institute, as the new transportation and communications secretary, and invited Tellez to serve as an adviser to help the presidency confront the economic crisis.

Tellez oversaw the investigation into the November 2008 plane crash that killed 15 people, including Interior Secretary Juan Camilo, when the jet smashed into a wealthy Mexico City neighborhood. A preliminary investigation found the pilots belatedly followed the control tower's instructions to reduce speed, and flew into turbulence in the wake of a Boeing 767-300 on the same flight path to Mexico City's international airport.

Tellez also had voiced the need for greater competition in the telecommunications industry.

Telefonos de Mexico SA, or Telmex, owned by the world's second-richest man, Mexican billionaire Carlos Slim, controls more than 90 percent of the nation's fixed phone lines, while his America Movil SA provides about 70 percent of cell-phone service in Mexico. Telmex also dominates Internet service, with 1.8 million high-speed accounts.

Before being named transportation secretary in 2006, Tellez was the managing director for the Mexican operations of the Washington-based global equity firm Carlyle Group. He also served as the former CEO of Desc, SA, one of Mexico's largest companies with nearly $2 billion in sales. The industrial conglomerate has businesses in the auto parts, chemicals, food production, brand management and real estate sectors.