At least 70 Guatemalan migrants have been reported missing in Mexico, the Foreign Ministry said.

"We have received about 70 reports about people who supposedly disappeared in Mexican territory," Foreign Ministry spokeswoman Andrea Furlan told reporters.

The majority of the cases involve people whose relatives last heard from them while they were passing through Tamaulipas, a state in northeastern Mexico where mass graves containing dozens of unidentified bodies have been found in the past few weeks, Furlan said.

The Guatemalan government sent Mexico information last week about 34 missing migrants feared among those killed and buried in the mass graves.

Only one Guatemalan migrant has been identified among those whose remains were found in the mass graves in San Fernando, Tamaulipas.

The man's remains will be repatriated once Mexican investigators finish gathering evidence in the case, officials said.

Guatemalan officials have asked relatives of the missing migrants to provide DNA samples and requested fingerprints from Mexico in an effort to try to identify citizens whose remains might have been recovered from the mass graves.

Mexican investigators found 40 mass graves containing the remains of 183 people in Tamaulipas in the past few weeks.

The victims are believed to have been kidnapped and murdered by Los Zetas, considered Mexico's most violent drug cartel.

Los Zetas has been blamed for several massacres in northern Mexico, including the killings last August of 72 migrants, the majority of them from Latin America, at a ranch outside the city of San Fernando.

The cartel has been battling rivals in several states for control of smuggling routes into the United States.

Los Zetas, in addition to trafficking drugs, is also involved in kidnappings, armed robberies and extortion rackets.

The flow of migrants has increased markedly in northeastern Mexico, especially Tamaulipas, since U.S. officials increased security along the border in the northwestern part of the country.

Last month, the National Human Rights Commission, or CNDH, Mexico's equivalent of an ombudsman's office, identified 71 cities in 16 of the country's 32 states that are considered dangerous for Mexican and foreign migrants headed to the United States.

"Kidnappings, abuse, extortion, robberies and sexual attacks on migrants have been documented" in the 71 cities, the CNDH said in a statement.

An estimated 300,000 Central Americans and 400,000 Mexicans undertake the dangerours journey across Mexico each year on their way to the United States.

About 20,000 Central Americans were kidnapped by organized crime groups, which extorted money from them or forced them to join their gangs, the CNDH said in a report released last year.