09/10/2011 07:46 EDT | Updated 11/10/2011 05:12 EST

Three women arrested after blocking entrance to drill site in Alberta

STANDOFF, Alta. - Three women who refused to move from the entrance of an oilfield drilling site on an Alberta First Nation have been released by police after spending a night in jail.

Lois Frank, one of the women who was arrested, says she is concerned about the environmental effects of hydraulic fracturing, also known as fracking.

The Blood Tribe's resources company has granted Murphy Oil permission to drill wells and at sites on their reserve south of Calgary.

The company says it may undertake fracking if the drilling proves successful.

Fracking involves injecting a mixture of chemicals, water and sand into the ground to help release gas and oil.

Frank says the band council granted the permission without adequate consultation and protesters want more answers about what chemicals will be used.

Blood Tribe police chief Lee Boyd says negotiations are underway between the band council and Murphy Oil so that protests at the site can occur legally.

Murphy Oil said in a report to the community earlier this year that safeguards are being put in place to make sure water wells won't be harmed by the fracking. It also said it would use cement casings in the wells it drills to protect groundwater.

Last month, Southwestern Resources Canada put all seismic testing in New Brunswick on hold because of ongoing protests over shale gas development, where fracking is used.

Quebec halted its fledgling shale-gas industry earlier this year following recommendations in an environmental-assessment report that advised the province to conduct more studies on the ecological risks.

Alberta's New Democrats are calling for an investigation into fracking.