Mexico said Monday that it had asked Israel to detain a former top investigator into the murky disappearance of 43 students in 2014 in a case that shocked the country.

Tomas Zeron, who was head of the Criminal Investigation Agency, is wanted over allegations of serious irregularities in the probe into one of the country’s worst human rights tragedies.

In July, Mexico said Zeron was in Canada and that it was seeking his extradition, but President Andres Manuel Lopez Obrador said Monday that he was now believed to be in Israel.