Parents of 43 students who disappeared in southern Mexico at the hands of police and a drug gang have lifted a protest camp in the capital.

They call it a show of faith in a new investigation after victims' relatives, international experts and human rights advocates cast doubt on a previous probe.

Lawyer Vidulfo Rosales said Tuesday the families hope it signals "a good start for a good stage of the investigation."

Interior Department deputy secretary for human rights Roberto Campa announced on Monday the creation of a specialized investigative unit. He called it a "fresh group" of investigators and said it came in response to parents' request.

The 43 teachers' college students were taken by police in Guerrero state in September 2014 and have not been heard from since.