SAN DIEGO -- A magnitude 4.4 earthquake struck the Imperial Valley and eastern San Diego County Monday, according to seismologists at the U.S. Geological Survey.

Monday's quake was centered further south than most other aftershocks from the magnitude 7.2 Easter Sunday earthquake which killed two people in Mexicali and caused about $100 million damage north of the border, according to USGS data.

Monday's temblor was centered about 60 miles south-southeast of Mexicali, and 50 miles north of the resort town of San Felipe, on the Sea of Cortez coast. It hit at 2:30 a.m.

That data would place it about 150 miles east-southeast of downtown San Diego. USGS computers originally estimated it was magnitude 3.4, but a human review of the data showed it to be magnitude 4.4

U.S. scientists have said their estimates of quake size and location are hampered in Mexico, because there are no real-time seismographs there.

Thousands of aftershocks have rattled the area since a magnitude 7.2 earthquake struck April 2.