Federal health and safety regulators have opened an investigation into an explosion and fire at an eastern Montana oil recycling facility that injured three workers.
    
Department of Labor spokeswoman Deanne Amaden says investigators from the Occupational Safety and Health Administration are at the Custom Carbon Processing salt water disposal and oil reclamation facility near Wibaux.
    
Amaden says the investigators will look at whether the company was following safety procedures and whether the blast could have been prevented.
    
Saturday's explosion happened as the contents of a tanker truck were being pumped into the facility. The tanker was still on fire Wednesday.
    
Wibaux Fire Chief Brian Nelson says an attempt to extinguish the flames was unsuccessful and firefighters are waiting for the blaze to burn itself out.