NASHVILLE (AP) — Handwritten notes from the state worker who supervises Tennessee's regulation of oil and gas production derided opponents of the hydraulic fracturing method of gas drilling as "stupid."

State documents obtained by WTVF-TV (http://bit.ly/R4W0HV) show the notes were written on emails sent to the Tennessee Department of Environment and Conservation when it solicited public comment on new rules to regulate hydraulic fracturing. Also known as fracking, the process extracts natural gas from rock by injecting high-pressure mixtures of water, sand or gravel and chemicals.

Michael Burton acknowledged making the notes and said they weren't intended to go public. He said he was venting his frustration on paper and apologized.

A TDEC statement said the department disapproved of Burton's remarks and talked to him about them. Burton hasn't been formally disciplined.