CHARLESTON, W.Va. (AP) — Troubled coal producer Massey Energy Co. took legal action against the industry's chief safety regulator for the second time in a week yesterday.

Richmond, Va.-based Massey said it is appealing a federal Mine Safety and Health Administration order covering what the company is allowed to do during the investigation of a deadly explosion at its Upper Big Branch.

MSHA won't allow the company to use cameras, coal dust analysis and other tools to investigate the April 5 explosion, which killed 29 men at the southern West Virginia mine. It is the worst U.S. coal industry disaster in 40 years.

"It is troubling that MSHA would seek to limit the ability of investigators to locate and analyze important evidence that is essential in determining the cause of the Upper Big Branch mine accident," Massey general counsel Shane Harvey in a prepared statement. "MSHA's actions imply that the agency does not want a thorough, objective and inclusive inquiry."

The company said it has appealed to the Federal Mine Safety and Health Review Commission, which handles disputes over citations and orders issued by MSHA over alleged violations of safety regulations.

MSHA said the order was developed and agreed upon with four of the five parties conducting the civil investigation of the explosion. The U.S. Department of Justice is conducting a separate criminal probe.

"These rules were put in place to ensure that evidence is not disturbed during the sampling or mapping process and were agreed to by all participating parties including the United Mine Workers of America and Gov. Joe Manchin's review team except Massey," MSHA spokeswoman Amy Louviere said. "Any accident investigation, especially one with a criminal component, must be conducted with painstaking care."

Massey is welcome to make suggestions about sampling and photos, Louviere said.

Massey already is facing off with MSHA in a separate federal lawsuit. Massey sued the agency last Tuesday in an attempt to limit its oversight of mine ventilation plans. The company has accused MSHA of forcing it to follow the agency's plans. Modern mines rely on ventilation to dilute methane gas, the suspected cause of the Upper Big Branch explosion.