Two former mariners have admitted their roles in a years-long credential test-fixing scheme.

The Department of Justice announced on Monday that Alexis Bell and Michael Wooten pleaded guilty to conspiracy to defraud the US. Authorities said the two acted as intermediaries between merchant mariners willing to pay for false test scores and US Coast Guard exam centre employees.

They both had scores fixed — Bell for one mate certification and Wooten for three engineer certifications.