( CNN ) -- Maricopa County , Arizona , Sheriff Joe Arpaio said Tuesday he shrugged off reports of a $ 1 million bounty on his head by Mexican drug cartels , saying this is not the first -- nor the largest . Arpaio , who calls himself `` America 's toughest sheriff , '' told CNN he had a $ 5 million bounty on his head when he worked for the Drug Enforcement Administration in Mexico . `` It 's nothing new , '' Arpaio said on CNN 's `` American Morning . '' `` It 's part of my job . They keep coming after me . '' Maricopa County Sheriff 's Office spokeswoman Lisa Allen said Monday that authorities are investigating the threat , which came in the form of a text message from a throwaway cell phone in Mexico . Allen said that the message was sent to a `` text message tree , '' similar to a phone tree . The message offered $ 1 million to anyone who could kill Arpaio . She said investigators `` do n't know how likely it is '' they will be able to track down the sender . It was not clear how the threat came to light . Allen said the FBI is assisting in the probe , but FBI special agent Manuel Johnson , a spokesman for the bureau 's Phoenix office , said the agency is aware of the reported threat but he knows of no federal investigation . Johnson said the bureau would help if Arpaio 's office requested assistance . Arpaio is well-known for creating a tent city jail in the Arizona desert , providing pink underwear for inmates and bragging that he spends more to feed his dog than a prisoner in his jail . He made national headlines for his tough enforcement of Arizona 's anti-illegal immigration laws and for his outspoken support for a new state immigration law , parts of which were blocked by a federal judge last week . His critics say he has a long history of abusing his power and launching bogus criminal investigations against political opponents . Those critics note that while the probes were launched with great public fanfare , they rarely resulted in convictions . A federal grand jury is probing the complaints , but Arpaio 's allies have defended the investigations as necessary . The 78-year-old sheriff , who has been the chief law enforcement officer for the county that includes Phoenix and many of its suburbs since 1992 , would not discuss the issue with CNN in a July interview , citing the federal probe . Arpaio was elected Maricopa County sheriff in 1992 and has been re-elected every four years since . He served for 32 years in federal law enforcement before then , ultimately becoming head of the DEA 's Arizona office . Speaking Tuesday on `` American Morning , '' Arpaio said the latest threats come with the job . `` It 's part of my work , '' he said . `` I do my job . Nothing changes . ''
$ 1 million bounty was sent as a text message , the sheriff 's office said . Threat originated in Mexico , sheriff 's spokeswoman says . Sheriff Joe Arpaio said he 's had previous death threats , including a $ 5 million bounty . ` Comment: