A group of Brazilian doctors have been accused of using silicone thumbs to clock-in co-workers at punch clock scanners that use fingerprint technology while the doctors were not at work.

One of the doctors, Thauane Nunes Ferreira, was allegedly filmed using the fake fingers to punch-in three colleagues who were not present at the Mobile Emergency Care Service clinic, known as Samu, in the city of Ferraz de Vasconcelos outside Sao Paulo.

City officials say as many as 11 doctors at the clinic were involved in the scheme in addition to as many as 20 nurses and ambulance drivers working at the mobile care facility.

Ferreira was discovered with six silicone thumbs on her person in addition to printout receipts indicating the time the absent doctors "clocked-in" to work at the biometric scanner.

She was arrested on Sunday after an anonymous tip led investigators to her.

The Municipal Secretary of Public Safety, Carlos Cesar Alves, said Ferreira, who faces charges of falsifying public documents, said she was following orders from a supervisor at the clinic, Jorge Cury.

According to Alves the medical workers and staff had to turn over the extra salary earned from the un-worked shifts to Cury via a bank transfer in return for a more "flexible" work schedule.

Ferreira's lawyer, Celestino Antunes, says his client was only doing as she was told. Cury, a long-time city employee, has called the charges "absurd."

He has not been charged with any crime, but investigators are looking into the case which has led to a larger investigation of "ghost-workers" city-wide.

Presented by Adam Justice