All foreigners are fingerprinted when they arrive in Japan
A Chinese woman managed to enter Japan illegally by having plastic surgery to alter her fingerprints, thus fooling immigration controls, police claim.
Lin Rong, 27, had previously been deported from Japan for overstaying her visa. She was only discovered when she was arrested on separate charges.
Tokyo police said she had paid $15,000 (£9,000) to have the surgery in China.
It is Japan's first case of alleged biometric fraud, but police believe the practice may be widespread.
Japanese police suspect Chinese brokers of taking huge sums to modify fingerprints surgically.
Local media reports said Ms Lin had undergone surgery to swap the fingerprints from her right and left hands.
Skin patches on her thumbs and index fingers were removed and then re-grafted on to the matching digits of the opposite hand.
Japanese newspapers said police had noticed that Ms Lin's fingers had unnatural scars when she was arrested last month for allegedly faking a marriage to a Japanese man.
The apparent ability of illegal migration networks to break through hi-tech controls suggests that other countries who fingerprint visitors could be equally vulnerable - not least the United States, according to BBC Asia analyst Andre Vornic.