MEDFORD, Okla. (AP) — Three small earthquakes have been recorded in northern Oklahoma during the weekend.

The U.S. Geological Survey reports the strongest was a magnitude 3.1 quake recorded at 7:22 a.m. Sunday six miles east of Medford, 77 miles south of Wichita.

No injuries or damage are reported.

The agency also recorded a magnitude 2.7 quake six miles southeast of Waukomis at 8:13 a.m. Sunday and a magnitude 2.7 temblor 12 miles northeast of Helena at 10:22 p.m. Saturday.

The number of magnitude 3.0 or greater earthquakes has skyrocketed in Oklahoma, from a few dozen in 2012 to more than 900 last year. Scientists have linked the increase to the underground disposal of wastewater from oil and gas production and state regulators have asked producers to reduce wastewater disposal volumes.