TULSA, Okla. (AP) — The Occupational Safety and Health Administration has issued citations to three companies involved in a natural gas rig explosion in Oklahoma that killed five workers.

OSHA announced Monday that it's fined Patterson-UTI Drilling, Crescent Consulting LLC and Skyline Directional Drilling LLC a total of $118,000 for "exposing employees to fire and explosion hazards" in the Jan. 22 explosion near Quinton, about 100 miles (160 kilometers) southeast of Tulsa.

An initial state regulator incident report indicates the blast happened when an uncontrolled release of gas caught fire.

Patterson-UTI officials say they disagree with the findings and have filed a notice of contest.

A Crescent Consulting representative declined to comment. SkyLine officials didn't return requests for comment.

The families of the five men who were killed have filed wrongful-death lawsuits.