GLENROCK, Wyo. (AP) — More than 60 residents have evacuated their homes after a natural gas leak at an oil well being drilled into the Niobrara (NYE'-oh-BRER'-uh) formation in Wyoming.

Natural gas has been spewing into the air from the oil well since Tuesday. Witnesses told television station KCWY-TV that the roar of escaping gas could be heard six miles away.

The town of Douglas is not threatened, since it is about 10 miles northeast. Well operator Chesapeake Energy says air samples are normal but the company asked about 80 residents who live within 2.5 miles to voluntarily evacuate.

Chesapeake officials say they are working with contractors to bring the well under control.

The Niobrara is a deep oil deposit beneath Wyoming, Colorado and Nebraska where drilling has increased over the past two year