The Registry of Motor Vehicles worker who authorities say scammed dozens of illegal immigrants out of thousands of dollars — promising licenses she never gave and delays in deportation she couldn’t deliver — is an example of fraud that one federal official warns isn’t going away, because the demand isn’t either.

“Documents are such a crux of what they need, it’s just so significant,” Bruce M. Foucart, special agent in charge of Homeland Security Investigations in Boston, said of illegal immigrants. “They’ll go to no end to get them. There’s a chance for people who are working at DMVs to be part of public corruption, to take a bribe or sell these at total gain for them. It’s always going to be there.”