BEIJING, June 8 -- Shanghai transport authorities are warning taxi riders to watch out for cabbies who try to charge them for bridge and tunnel tolls that haven't been levied for years.

    Dozens of commuters - mostly foreigners and other visitors - have been victimized, authorities said.

    "Some cabbies are taking advantage of the fact that out-of-town passengers are ignorant about local conditions, and it's ruining the reputation of the city's entire taxi industry," said Wu Runyuan, a spokesman for the Shanghai Urban Transport General Law Enforcement Team.

    The scam is being committed by taxi drivers who adjust their meters to print fees for nonexistent tolls.

    Some cabbies cover their tracks by erasing the meter's data bank and by not giving riders a receipt.

    In a May 18 case, a foreigner took a taxi from the Longyang Road Station of Metro Line No. 2 to Pudong International Airport. When he arrived, the meter showed a charge of 67 yuan, but the driver added another 80 yuan for tolls.

    Later last month, a taxi took another foreigner from the Sofitel Hyland Shanghai on Nanjing Road E. to the Pudong airport. The fare was 141 yuan, but the driver then keyed in another 200 yuan for tolls.

    The foreigner paid but learned later from Chinese friends that he'd been cheated.

    Officials said they have received dozens of complaints and punished several taxi drivers. Precise figures weren't released.

    Some of the drivers were suspended for 15 days. The improper use of a taxi meter can also lead to a 2,000 yuan fine.

    Authorities said taxi passengers can refuse to pay the fare if a driver asks for toll fees or if one is written on the receipt. Riders are also advised to write down the numbers of the driver's ID and the cab's license plate and report the incident via the 12319 hotline.