An employee for an independent MBTA subcontractor was arrested Thursday for allegedly selling millions of dollars worth of unauthorized T passes.

Since 2007, Andres Townes, 27, of Revere, produced thousands of Charlie Cards worth just under $5 million and sold most them online through Craigslist for a discount, officials said.

“He is charged with what is believed to be the largest scheme of illegally produced passes,” said Attorney General Martha Coakley.

Townes worked for Cubic Transportation Systems of Beverly, which fulfilled online and phone orders for the majority of T monthly passes. As a fulfillment supervisor there, Townes had access to the secure room that houses the machines to produce the cards.

Authorities showed one of the illegal cards he allegedly produced. Its value was $235, but he sold it online for $200, they said.

Because at least hundreds of T riders bought their passes this way, the agency lost potentially millions in revenue.

T GM Rich Davey said T supervisors are now monitoring the production at Cubic. Fare terminals will also be audited.

“I think what escaped us here was the volume. Even a couple of hundred tickets a month would be difficult to detect,” Davey said.

Davey said he sent a letter to the company in an attempt to terminate the $2.3 million annual contract and expressed “outrage” over the incident. He added that the T believes it can recoup the lost revenue.

The fraudulently produced passes have been deactivated and authorities said they do not believe anyone else is involved.

The investigation is ongoing and the scope is still being determined.

Worker’s diligence pays off

An alert Commuter Rail conductor who spotted a discolored monthly pass broke up the scheme.

The rider told the conductor that the pass went through the laundry and authorities said it actually did.

However, when the conductor brought the pass to authorities it was discovered that there wasn’t a serial number associated with the card, which triggered a two-month investigation.