A local Chinese government acknowledged Wednesday that officials knew about melamine-tainted eggs for a month before the contamination was publicly disclosed.

The revelation was the latest in a growing scandal over food products tainted with the industrial chemical and followed the recent disclosures that Chinese authorities and a leading dairy producer also delayed reporting for months that baby formula had been tainted with melamine. The contamination caused kidney stones in babies and was blamed for killing four infants and sickening 54,000 children. More than 3,600 children remain sick, health officials say.

A brand of chicken eggs from China's leading egg processor, Dalian Hanwei Enterprise Group, was pulled from some stores last week after Hong Kong food safety regulators found excessive levels of melamine in the company's eggs.

Authorities in the eastern city of Hangzhou recalled another company's eggs while Hong Kong's government said tests on eggs from two more processors found excessive amounts of melamine.

Hanwei's Web site said that besides the domestic and Hong Kong markets, its egg products are exported to Japan and Southeast Asia. China's fresh eggs are mainly exported to the Chinese territories of Hong Kong and Macau, while processed egg products are sold to Japan and the U.S., according to a February egg market report on the Agriculture Ministry's Web site, the latest available report.

The government of Dalian, the northeastern port city where Hanwei is based, said in a notice dated Wednesday that it was first alerted to the problem of melamine-tainted eggs more than a month ago — but it did not explain the apparent delay in publicly reporting the problem. The city government said they were investigating how eggs came to be contaminated with melamine.

Hong Kong authorities were the first to report the problem with Hanwei's tainted eggs over the weekend.

The widening food scandal has exposed the inability of Chinese authorities to keep the food production process clean of melamine, despite official pledges to raise food safety standards.

There have not been any reports of people being sickened by contaminated eggs, and it was not immediately clear how many eggs had been recalled.

But the problem was affecting sales. In Beijing, egg sales dropped at least 10 percent Tuesday at the Xinfadi Wholesale Market, a major distribution center in the capital, the official Xinhua News Agency said.

"Everyone is scared of eating eggs right now. Who knows what other types of food is affected?" said Wen Hu, a 28-year-old software engineer in Dalian."All of my co-workers, friends and family, not just those living in Dalian, have stopped eating eggs. It's one of those things that it is better to be safe than sorry."

The Dalian city government's notice said it was likely melamine had been added to the feed given to the chickens that laid the eggs.

Melamine is used in making plastics and fertilizer, and is banned from animal feed. One food industry expert said it was likely added for the same reason cited in the milk scandal and last year's recall of tainted pet food: Melamine boosts nitrogen levels, making products seem higher in protein when tested.

Han Wei, director of the company, was quoted by Xinhua as saying Hanwei "has never bought melamine or added it to the feed." He said melamine had been found in some stored feed supplied by a feed plant in late September. No other details were given and telephones at Hanwei were not answered.

The Dalian government notice said local authorities were notified Sept. 27 of tests by the customs bureau of Liaoning province that had found melamine in a batch of export-bound eggs produced by Hanwei.

The city government said it immediately ordered Hanwei to recall the eggs deemed "problematic" and temporarily halt its egg exports. By Oct. 5, seven shipping containers that had reached Hong Kong carrying Hanwei's eggs had been recalled, while two other containers that stayed in Hong Kong were sealed off.

The recalled eggs were destroyed to prevent them from entering the domestic market, the notice said, while further tests on other batches of eggs from the company did not detect melamine.

Meanwhile, more tainted eggs turned up in Hong Kong and the mainland.

Hong Kong's government said late Wednesday that tests on eggs processed by Jingzhou Shuanggang Poultry Breeding and Processing Co. Ltd. in central Hubei province found excessive levels of melamine. It said a few hours earlier that tests on eggs from Jingshan Pengchang Agricultural Product Co., also in Hubei, showed elevated levels.

Authorities in the eastern Chinese city of Hangzhou, meanwhile, recalled a brand of eggs produced by Green Living Beings Development Center of northern Shanxi province, Xinhua.