A new study suggests that wastewater wells are linked to an increase in seismic activity in Colorado and New Mexico.

Researchers believe that wastewater injected deep underground is responsible for the significant rise in the number of earthquakes in the region since 2001, Phys.org reported.

The study focused on the Raton Basin, which stretches from southern Colorado into northern New Mexico. This area was seismically quiet until shortly after major fluid injection began in 1999. But records show that since 2001 there have been 16 earthquakes with a magnitude of at least 3.8, compared to only one in the previous 30 years.

According to the researchers, the increase in earthquakes is limited to the area of coal-bed methane production and within 5 kilometers (3.1 miles) of wastewater injection wells associated with this activity.

They found several lines of evidence indicating that the earthquakes are directly related to the disposal of wastewater, a by-product of extracting methane, and not to hydraulic fracturing in the area.

According to the U.S. Geological Survey (USGS), there are more than 150,000 Class II injection wells in the United States. Of these, around 40,000 are waste fluid disposal wells for oil and gas operations and only a small fraction of them have induced earthquakes that are large enough to be of concern to the public.

The new study will be published in the Bulletin of the Seismological Society of America (BSSA).