MEXICO CITY - Mexico has become the Western Hemisphere's hot spot for "enforced disappearances," in which police or the military arrest citizens who are never seen again, Human Rights Watch said Wednesday.

The advocacy group said it had documented 149 cases throughout the country in which witnesses saw police or soldiers take someone into custody, only to have the person vanish without a trace.

Human Rights Watch called on President Enrique Peña Nieto's 11-week-old administration to create a database of missing people and take other urgent steps to address "the most severe crisis of enforced disappearances in Latin America in decades."

In a withering report, the New York-headquartered group said the number of Mexicans who had vanished since 2006 was enormous, noting that a provisional list compiled by the Attorney General's Office indicated that more than 25,000 people had disappeared during the government of former President Felipe Calderón, who left office Dec. 1 and is now a visiting fellow at Harvard University's Kennedy School of Government.

The group said it had probed 249 cases in depth and found that 149 of them implicated security and law enforcement agents in the disappearances.

"These crimes were committed by members of every security force involved in public security operations, sometimes acting in conjunction with organized crime," the report says. The Calderón administration "ignored this mounting 'disappearance' problem," and Mexican authorities "failed to take serious steps to address it," it says.

Neither Peña Nieto, who was traveling in Costa Rica, nor his top security aides offered an immediate response to the 176-page report, titled "Mexico's Disappeared: The Enduring Cost of a Crisis Ignored." Calderón has argued that his frontal attack on drug gangs helped restore order to the country.

Human Rights Watch said the disappearances it had investigated usually followed the same pattern:

"In many cases, these detentions occur in victims' homes, in front of family members; in others, they take place at security checkpoints, at workplaces or in public venues, such as bars," the report says. "When victims' relatives inquire about detainees' whereabouts at the headquarters of security forces and public prosecutors' offices, they are told that the detentions never took place."

The report notes that in at least 20 disappearances of Mexicans in June and July 2011, naval personnel were implicated. The United States works closely with the Mexican navy on drug cases.

In an additional 13 cases, the Federal Police made the initial arrests. State, local and army units were fingered in the remainder. In more than 60 cases, security forces appeared to be working in tandem with organized crime groups, it said.

As many as 3,000 Mexicans are thought to have disappeared during the country's so-called dirty war in the 1960s and '70s.