The body of Alberto Lopez Bello, a 28-year-old journalist with the daily El Imparcial, was discovered near a stream west of the city, said Manuel de Jesus Lopez, the top prosecutor for the state of Oaxaca.
"Unfortunately, we can confirm that one of the dead is the crime reporter Alberto Lopez Bello of El Imparcial," Jesus Lopez said.
The prosecutor could not confirm whether the crime was related to Lopez Bello's work as a journalist.
Lopez Bello had been working with El Imparcial for the past six years and had gone to work yesterday, a colleague at the newspaper told AFP.
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Mexico has endured an onslaught of drug-related violence that has left 70,000 people dead since 2006, making it one of the most dangerous countries for journalists in the world.
At least 84 media workers have been murdered and 20 more have gone missing since 2000, according to the National Human Rights Commission.
The journalist was briefly detained by police in May when he and a colleague were taking pictures of a sign put up on a bridge by a gang in Oaxaca, a human rights group said.