A magnitude 6.4 earthquake struck northern Argentina early on Monday, the U.S. Geological Survey said. The quake occurred at 2:07 a.m. local time (0507 GMT) and was centered 72 miles (116 km) east-southeast of Santiago del Estero, the USGS said. There were no immediate reports of injuries or damage from the quake, which was upgraded from an initial 6.3.