A Pennsylvania candy maker did not evacuate workers even after some reported smelling gas before an explosion that killed seven employees in March, the Department of Labor said on Thursday.

The agency's Occupational Safety and Health Administration found in its investigation that the company, R.M. Palmer, did not have workers exit its manufacturing plant even after some voiced worries about what the Occupational Safety and Health Administration later determined was a natural gas leak.

"Seven workers will never return home because the R.M. Palmer Co. did not evacuate the facility after bring told of a suspected gas leak," OSHA Area Director Kevin Chambers in Harrisburg, Pa., said in a statement. "The company could have prevented this horrific tragedy by following required safety procedures." 

An additional 10 workers were injured in the explosion, which leveled a building in the factory complex and damaged several other buildings in West Reading, Pa., a small town 60 miles northwest of Philadelphia.

A machine operator pulled alive from the rubble said she might not have survived if not for falling into a vat of liquid chocolate, which extinguished flames burning her arm, according to the Associated Press. Patricia Borges, 50, said she and others had complained about a gas odor about 30 minutes before the factory exploded.

The National Transportation Safety Board (NTSB) determined that a natural gas leak had cause the March 24 blast and fire in preliminary findings released in May and updated in July.  

R.M. Palmer said in a statement to CBS MoneyWatch that it "continues to cooperate in the NTSB's investigation," but also intends to "vigorously contest OSHA's citations, which it believes are legally and factually unsupported." The company, which has been in business since 1948 and has about 850 employees, also said it is "still mourning the tragic deaths and injuries to its employees."