The helicopter was attempting to land at an airfield in Santiago Jamiltepec when it crashed in a nearby field on top of two vehicles, a spokeswoman for the Oaxaca attorney general's office told CNN.The 13 who were killed were all on the ground, spokeswoman Lizbeth Hernandez Bravo said. Twelve died at the crash site, while one died later at the hospital, the state attorney general's office said. Three of the dead were children, the office said. Fifteen others were injured. The helicopter was surveying the damage from the quake, and was carrying Mexican Interior Minister Alfonso Navarrete Prida and Oaxaca's governor, Alejandro Murat. Both men survived and only suffered "slight concussions," the Interior Ministry tweeted. The 7.2 magnitude earthquake and a magnitude 5.8 aftershock — both with epicenters in Oaxaca state — struck the region Friday, the US Geological Survey reported. Mexican President Enrique Peña Nieto said the crash took place while the helicopter was landing."Unfortunately, people on the ground lost their lives and others were wounded. My condolences to their families and my wishes for a prompt recovery to those injured," the President tweeted.When addressing the helicopter crash on Twitter, Peña Nieto said there were no reports of fatalities directly linked to the quake and aftershock.Efrain de la Cruz, mayor of Santiago Jamiltepec, was on the phone with CNN en Español's Mario González when the crash occurred. "A helicopter carrying the governor and the others went down," he said."A helicopter is down, a helicopter is down. Oh my God! It's a military helicopter," Cruz said. "This can't be possible, oh my God."
CNN's Mariano Castillo, Nicole Chavez and Florencia Trucco in Atlanta and Leyla Santiago in Mexico City contributed to this report.