A magnitude 5.4 quake struck Mexico's Baja California on Saturday morning, very close to the northern city of Mexicali, Reuters quoted the U.S. Geological Survey sources as saying. It said the very shallow quake, only 4.3 miles (7 km) deep, was centered only 16 miles (26 km) southeast of Mexicali, a city with an estimated population of one million people. There was no immediate indication of damage or casualty.