Four officials in Shanghai have been punished for dereliction of duty in relation to a recent food safety scandal involving steamed buns, local authorities said Friday.

A deputy director of food production supervision agency in Shanghai's Baoshan district was removed from his post, a joint investigative team said in a statement.

Two other officials of the agency and a deputy director of the district's quality and technology supervision bureau were given disciplinary punishments, it said.

Police had earlier arrested five managers of a steamed bun production factory that was involved in adding illegal chemicals to steamed buns for the purpose of deceiving customers.

Managers at the Shanghai Shenglu Food Co. subsidiary in Baoshan district confessed to the illegal production and sale of 334,864 dyed steamed buns worth a total of 200,000 yuan ($30,860) since January of this year.

Shanghai municipal government authorities have also ordered the city's large chain supermarkets to create their own food safety departments.

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 its workers re-labeled 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 in order to create "new" buns.