The U.N. human rights office has “strong indications” that Mexican federal security forces are behind a series of disappearances around Nuevo Laredo, a city on the U.S.-Mexico border, officials said on Wednesday.

In a statement, United Nations High Commissioner for Human Rights Zeid Ra’ad Al Hussein urged the Mexican government to "take urgent measures to stop the wave of forced disappearances in Nuevo Laredo and surrounding areas," amid allegations that federal security forces in Mexico are behind such disappearances.

The U.N. Human Rights Office in Mexico documented the disappearance of 21 men and two women in Nuevo Laredo from February until May 16, but local human rights organizations said there have been at least 40 disappearances in this period.

“Many of these people are reported to have been arbitrarily detained and disappeared while going about their daily lives,” Zeid said.

A series of testimonies received at the the U.N. human rights office suggest that people currently missing were reportedly detained by uniformed personnel as they walked or drove along public roads, and several burnt out and bullet-ridden vehicles were found by the roadside, the statement said.

"It is particularly horrific that at least five of the victims are minors, with three of them as young as 14. These crimes, perpetrated over four months in a single municipality, are outrageous,” said Zeid.

The U.N. report is the latest finding by international groups highlighting alleged abuses by the government in its decadelong battle against criminal gangs.

More than 35,000 people have gone missing since President Felipe Calderón sent military forces to battle drug gangs in late 2006.

There have been more than 200,000 murders since then, with a record number last year fueling widespread anger with President Enrique Peña Nieto’s ruling party ahead of a July 1 presidential election.

Mexican authorities had ample information and evidence about the Nuevo Laredo disappearances but had made little progress in investigating — leaving the burden of the search to the family and friends of some of the people missing, the U.N. noted.

"Families have undertaken their own searches, without any protection, and relatives have to date found the bodies of at least six victims. Several witnesses have been subjected to threats, and one was disappeared for two days," the statement read.

Mexico’s National Human Rights Commission, better known by their Spanish acronym CNDH, released a statement on Wednesday saying they initiated an investigation looking into the disappearances and described efforts such as asking the Navy and other officials to protect the population of Tamaulipas, the Mexican state where Nuevo Laredo is, though at least three disappearances had happened since then.

While CNDH's statement detailed steps the government was taking, it didn't include any findings or potential leads that could possibly give families of the victims some closure.

“It is vital the Mexican authorities carry out an effective search for those whose whereabouts are still unknown and to conduct a diligent, independent and complete investigation to find out what happened, identify those responsible and ensure they are brought to justice,” Zeid said.