At least three people died when their helicopter crashed in Mexico's southern state of Oaxaca, local media reported.The helicopter, which crashed on Friday in the town of San Martin de Porres, belonged to Mexico's telecom giant Telmex, Xinhua reported citing the daily El Universal.Four people were onboard the aircraft at the time of the incident, and the lone survivor was sent to a nearby hospital for treatment.Citing a press release from the Oaxaca state government, the daily said initial reports indicate weather conditions caused by a cold front caused the crash.The helicopter was carrying out routine service on a telephone service module, the daily said.