Twenty-nine suspects were arrested and 20 of them were held in criminal detention for manufacturing and selling water-injected beef, local police in Nanjing, Jiangsu province, said on Wednesday.

Law enforcement officers are still tracking and recovering water-injected beef that has entered the market, according to the Nanjing public security bureau.

Local residents reported to the media in August that some of the beef being sold at Runheng meat and frozen food markets was cheaper than other markets, and suspected that it was water-injected. Jiangsu Broadcasting Corp then sent reporters, who spent three months investigating. It said they confirmed that the cattle were brutally treated before being slaughtered.

Video reports from the media group showed the cattle being injected with water through plastic pipes inserted through the animals' noses and into their stomachs at slaughterhouses in Lai'an and Quanjiao counties in neighboring Anhui province.

A man said in the video report that the animals were injected several times, usually starting 12 hours before they were killed. Around 60 kilograms of water would be injected into each one.

"We felt sad when we saw the scene," he said. "But we would lose our job if we didn't do it."

The boss of one factory, surnamed Xu, said in a video interview that the cattle would be killed whether he injected water into them or not.

"The cattle didn't feel pain," he said.

After receiving reports from the media in early November, the police in Nanjing; and Chuzhou, the Anhui city that administers Lai'an and Quanjiao counties, joined forces to investigate the case.

They found 13 cows that had been injected with water and six slaughtered ones that had been water-injected at two slaughterhouses. They detained suspects responsible for manufacturing and selling the beef.

The substandard beef was delivered and sold at four markets in Nanjing, according to the Nanjing police. It had also been sent to some schools in the city.

Huang Ming, a professor at Nanjing Agricultural University's food science and technology school, said tainted beef could harm people's health and buyers can tell whether the meat is water-injected or not by looking at the color or touching the surface.

"The color of water-injected meat is light red, while the normal one is red or dark red," he said. "The surface of the water-injected meat is wet, and the meat is not flexible. If you put a napkin on top, it will become soaked quickly. The one on normal meat will stay dry."

Police said seized beef had been handed over to the Nanjing Agricultural Committee for disposal.

Zou Chenyang, a Nanjing middle school teacher, said the suspects' cruelty to the cattle made his hair stand on end.

"Animals should not be treated with such cruelty in a civilized society," he said. "As a vegetarian, I think that meat lovers should consider having less meat, and slaughterhouses should be equipped with pain-relief equipment."

Zhu Lixin contributed to this story.

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