A Shanghai court on Monday jailed three company officials for five to nine years for adding dye to buns, local media said, as China cracks down after a string of food safety scandals. The court sentenced three executives of the Shenglu Food Company, after they were found responsible for illegally adding yellow dye to a type of steamed bun made of corn flour, the Xinmin Evening News said. The company also re-sold old products by changing the expiry dates on packaging, the newspaper said on its website. The scandal came to light after state broadcaster China Central Television ran an expose in April this year which revealed the company's practices. Steamed buns are a staple breakfast food in China and the company's products were sold through two of Shanghai's biggest supermarket chains. The three executives -- the general manager, sales manager and production manager -- were also fined between 200,000 to 650,000 yuan each ($31,000 to $102,000). The court could not be reached for comment. Shanghai over the weekend announced rewards of at least 500 yuan to people who provide tips over food safety violations. After several high-profile food safety scandals, China is trying to crack down on violations to reassure citizens and restore faith in government. Earlier this month, the government arrested 32 people over the sale of cooking oil made from leftovers taken from gutters. One of the biggest safety scandals emerged in 2008 when huge amounts of the industrial chemical melamine were found to have been illegally added to dairy products to give the appearance of higher protein content. In September last year, authorities in China -- including the Supreme People's Court and the Ministry of Public Security -- called for tougher penalties including the death sentence in serious food safety cases.