A moderate earthquake struck northwestern Mexico near the U.S. border Monday, prompting authorities to evacuate schools and resulting in at least one minor gas leak.

No major damage or injuries were reported from the temblor, which an expert said was likely an aftershock from a magnitude-5.4 quake three days ago.

The magnitude-5.1 quake happened around 10:30 a.m. local time (1830 GMT). It was centered about 20 miles (35 kilometers) southeast of the border city of Mexicali, and 24 miles (40 kilometers) southeast of the U.S. border city of Calexico, California, according to the U.S. Geological Survey. The magnitude was revised upward from 4.9.

In Mexicali, an industrial border city of about 750,000, the quake caused the wall of a school to fall and started a gas leak in a second school, prompting authorities to evacuate all of the city's learning centers, said Alfredo Escobedo, civil protection director for the Mexican state of Baja California, which includes Mexicali. Escobedo said no injuries or other damages were reported.

On Friday, the Mexicali area was rocked by a magnitude-5.4 quake that shut down factories and left 400,000 people without power. That quake was felt in parts of California and Arizona, the USGS said.

The latest temblor was likely an aftershock, said Julie Martinez, a geophysicist at the National Earthquake Information Center in Golden, Colorado.

A series of smaller quakes, ranging from magnitudes 2.5 to 2.9, preceded Monday's temblor and there were at least five aftershocks, including one registering a magnitude-3.6, the USGS said.

In 2000, the northern Baja California region near Mexicali was rattled by a cluster of quakes, but they did not cause any damage.