Kenneth P. Katen, a federal mine safety official during the Reagan administration, said the groups would work together in the Sago investigation but release separate reports.
Sago's history of federal health and safety violations, which nearly tripled from 2004 to 2005, would immediately draw scrutiny, said J. Davitt McAteer, who was assistant Labor secretary for mine safety during the Clinton administration.
"The number of violations was increasing, not decreasing" at Sago, McAteer said. "The severity and importance of the violations were increasing. We're talking about issues such as roof control, ventilation, accumulation of combustible material."
Two areas that particularly troubled federal inspectors last year were the mine's ventilation plans and its placement of methane monitors. Katen and other mine safety experts say reports that the mine explosion originated in an unused section of shaft raise concerns that explosive methane gas might have built up.