BISMARCK, N.D. (AP) -- The Occupational Safety and Health Administration is investigating the cause of a drill rig collapse near Belfield in western North Dakota.
Neighbors Drilling spokesman Denny Smith tells the Dickinson Press (http://bit.ly/TTiY6Y  ) that no one was hurt and no fluids spilled when the rig's derrick collapsed Tuesday.
OSHA spokesman Eric Brooks says investigators obtained a warrant to enter the site on Thursday. Brooks say companies are allowed to force investigators to obtain a warrant under federal law. But he says it happens infrequently.
Smith says requiring OSHA to get a warrant is standard procedure for his company.
Smith says it's unknown whether the collapse was caused by a mechanical failure or human error.