Mexico is sending its national commissioner for missing persons to the northern border city of Nuevo Laredo after the U.N. said it documented the disappearance of 23 people there — likely at the hands of a security force.

Mexico' Attorney General's Office also opened an investigation after the Office of the U.N. High Commissioner for Human Rights asked about the situation.

The U.N. says there are strong indications a federal security force was responsible for the disappearances. Human rights advocates and victims' families in Nuevo Laredo blame marines.

The government's statement late Wednesday night said that its response to violence cannot come outside the law.

Jessica Molina says she had reported to the Attorney General's Office that her husband was taken by marines in March, but there was no follow-up.