MEXICO CITY, Sept 24 (Reuters) - Mexico has sent a letter to Israel"s government urging it to facilitate the extradition of a former Mexican official in charge of a controversial investigation into the disappearance of 43 student teachers seven years ago, a senior official said on Friday. Tomas Zeron, former head of Mexico"s criminal investigation agency, has since last year been in Israel, where he went to evade a probe into his handling of the investigation into the disappearances, according to Mexican government officials. Mexican authorities and relatives of the missing youths have accused Zeron of planting evidence to support the previous administration"s version of what happened to the 43 students after their abduction on the night of Sept. 26, 2014. Zeron, who could not be reached for comment, has previously denied that allegation. Deputy Interior Minister Alejandro Encinas said President Andres Manuel Lopez Obrador had sought the assistance of Israeli Prime Minister Naftali Bennett. "The president has sent a letter ... requesting (Israel"s)support and cooperation to expedite the extradition process of (Zeron)," Encinas said, noting Bennett had not yet received the letter. Israel"s embassy in Mexico was not available for comment. The trainee teachers went missing in the southwestern city of Iguala. The government said they were kidnapped by corrupt police in cahoots with a local drug gang. The last administration said the gang killed the students, believing some of them were working for a rival outfit, incinerated their bodies and tossed their ashes into a river. So far only the remains of two of the 43 have been definitively identified. A panel of international experts later picked holes in the official version, deepening anger over the scandal that stained the reputation of the former government. Lopez Obrador pledged to clear up the case when he ran for office in 2018.