 During the government of Ernesto Zedillo the government decided to modernize the prison system and Islas Marias was deactivated.On 27 November 2003 it was declared a biosphere reserve but with the prison system still existing.The prison situation in Mexico became so critical that the government announced in 2004 that they were reactivating the Islas Marias prison to transfer 2,500 prisoners from prisons all over the country.