Members of awell-known rodeo family who maintain a ranch in central Alberta say a sour gas leak from a nearby oilfield facility has made them and their horses sick.

Lynda Thurston told CBC News Friday she reported the leak at the Bearspaw Petroleum facility on Oct. 26, after the family arrived at their home near Big Valley to the smell of sour gas.

Thurston and her three teenage sons, who form the trick-riding trio known as The Thurston Gang, allege they experienced nausea, dizziness and tingling sensations that night.

She said the family's horses, needed for their rodeo and work on the cattle ranch, have been sick ever since. They have no energy and cannot be used at all.

This is the second leak from the facility this year, and the problems date back to 2001, she said.

Although this latest leak is under investigation by theAlberta Energy and Utilities Board, Thurston said she has lost confidence in the process.

Energy board spokesman Darin Barter said the board will look at what caused the leak and the company's response to it.

"Obviously any sour gas released into the atmosphere is very bad news," Barter said.

A mediation session between the company and the Thurston family will be held next week, he said.Energy board officials will also attend that meeting.

The company, Bearspaw Petroleum, was not available for comment.