The U.S. Geological Survey says it recorded seven small earthquakes in central Oklahoma in 14 hours over Saturday and Sunday.

According to an Associated Press story, the quakes ranged in magnitude from 2.6 to 2.9 on the Richter Scale.

Earlier on Saturday, four quakes were recorded in the same area of central Oklahoma. One of those quakes registered 4.3 on the Richter Scale.

No injuries or damage were reported.

Some residents in the area say they believe that drilling for oil may be the reason for an increase in seismic activity in the region.

According to the AP story, Austin Holland, a research seismologist with the Oklahoma Geological Survey, said the state is experiencing unprecedented earthquake activity and scientists are trying to determine whether the earthquakes are a natural phenomenon or are man-made.

For the full story, see The Associated Press.