SNC-Lavalin Group Inc., Canada’s largest engineering firm, is reeling from federal fraud and bribery charges filed Thursday by Canadian prosecutors, even after the company has spent three years implementing massive compliance reforms.

The company fired off a heated statement Thursday questioning why the charges were needed, saying they were without merit and that it would vigorously defend itself. The charges involve alleged bribery by former employees on projects in Libya. Some individuals already have been arrested and convicted.