Mexico’s top immigration official resigns amid growing security issues

Romero has been head of the National Institute of Migration since 2006. The Senate had summoned her to testify on what measures the office was taking to protect migrants moving through Mexico. No reason was provided by the Interior Ministry on her resignation.

The massacre discovered in late August of 58 men and 14 women from South and Central America trying to get to the US was widely condemned by Senators.

They acknowledged that Mexico could not "demand respect for its nationals in the United States" when it "does not assure the dignified treatment" of foreign migrants on its own territory.

Ms Romero, a former congresswoman from the ruling National Action Party, updated migrant holding centres and ensured that immigration agents were trained in human rights, the interior ministry said.

An unnamed official said the government was looking for someone with more experience in security experience as a result of the increasing involvement of drug cartels in illegal migration.

Prosecutors say evidence suggests "very strongly" that members of the Los Zetas cartel had killed the 72 migrants, whose bullet-ridden bodies were found at a ranch in the state of Tamaulipas on 24 August.