SHANGHAI - Three managers of a steamed bun production factory in Shanghai were officially arrested Tuesday for producing and selling shoddy products.

An investigation showed the general manager, sales manager and production manager of Shanghai Shenglu Food Co. were involved in adding coloring to lower cost and increase profit while producing corn flour buns at a subsidiary in Baoshan District, the prosecution said.

Last month, a deputy director of the food production supervision agency in Shanghai's Baoshan district was removed from his post for dereliction of duty.

Two other officials of the agency and a deputy director of the district's quality and technology supervision bureau were reprimanded.

The managers previously confessed to the illegal production and sale of 334,864 dyed steamed buns worth a total of 200,000 yuan ($30,740) since January.

The scandal emerged after China Central Television (CCTV) reported on April 11 that the plant had been adding coloring to make wheat buns look like corn flour buns and black rice buns.

CCTV also reported that workers relabeled buns made two days earlier with new production dates. These workers also added expired buns, which had been returned to the factory by retailers, to their mixers to create "new" buns.