A Brazilian doctor faces charges of fraud after being caught on camera using silicone fingers to sign in for work for absent colleagues, police say.Thaune Nunes Ferreira, 29, was arrested on Sunday for using prosthetic fingers to fool the biometric employee attendance device used at the hospital where she works near Sao Paulo.She is accused of covering up the absence of six colleagues.Her lawyer says she was forced into the fraud as she faced losing her job.The local public prosecutor's office opened an investigation on Monday.The doctor was arrested by the local police following a two-week investigation in the town of Ferraz de Vasconcelos, and was released on Sunday.Police said she had six silicone fingers with her at the time of her arrest, three of which have already been identified as bearing the fingerprints of co-workers.The town's mayor, Acir Fillo, has also asked five employees of the medical service said to have been involved to step aside, while the local council has launched a public inquiry into the matter.Brazil's ministry of health has said it will launch an inquiry of its own into the local hospital.Mr Fillo says that the police investigation showed that some 300 public employees in the town, whom he described as ''an army of ghosts'', had been receiving pay without going to work.A council spokesman has told BBC Brasil that among those believed to be those "ghost employees" - as Brazilians call informally those who receive regular wages without actually showing up for work - are public workers in the areas of health, education and security.