The U.S. Treasury Department has suspended cooperation with the Mexican government on financial investigations, a move that could potentially affect drug, money laundering and terrorism financing investigations.

The U.S. Embassy said the Treasury Department (search) sent a letter to the Mexican government saying that, because confidential U.S. information was leaked to the public during a political scandal here, it would no longer cooperate in cross-border investigations.

The letter said the suspension of cooperation, which began Thursday, would be in affect until there are "guarantees that all delicate information will be protected."

Mexican Attorney General Rafael Macedo de la Concha (search) said the move affects information about some 30,000 financial transactions daily, many of which are monitored by both the U.S. and Mexican governments for illegal activity.

The disagreement is over a U.S. report that apparently described dealings of the Mexico City finance director, Gustavo Ponce (search), who disappeared after clandestine videos of him gambling in Las Vegas were shown on Mexican television this month.

The videos were accompanied by reports — possibly from the U.S. document — describing Ponce's lavish spending in Las Vegas.

Mexico City Mayor Andres Manuel Lopez Obrador (search), embarrassed by the scandal, later waved a copy of the U.S. report during a news conference, saying it proved that federal authorities knew before he did that Ponce was corrupt but took no action.

Lopez Obrador was scheduled to appear before federal investigators later Friday.

Macedo denied that anyone in his department leaked the information, and he said he would investigate to see where the security breach occurred.

"We have to re-establish this flow of information," he said.