ARLINTON, Texas — Two new studies from University of Texas at Arlington researchers show harmful bacteria levels in groundwater near hydraulically fractured gas drilling sites.

The studies published in the peer-reviewed journal Science of the Total Environment show antibiotic-resistant bacteria exist in private water wells in the Barnett Shale and Eagle Ford Shale regions of Texas.

The researchers say these bacteria could cause gastrointestinal illnesses along with rashes and eye and ear infections.

But the studies make no definitive links between fracking and contaminated water.

Naturally occurring gas, agriculture waste or some combination could be the contamination sources.

Fracking has led to a boom in natural gas production but raised widespread concerns about possible groundwater contamination. The method uses huge amounts of pressurized water, sand and chemicals to break apart underground rock formations.