Shanghai police are investigating an online ad offering babies for sale on the Chinese subsidiary of auction Web site eBay (search), the company said Thursday.

The ad was deleted shortly after it was placed Sunday and relevant information has been turned over to investigators, a spokesman for the Eachnet (search) Web site said.

"We took measures as soon as we received complaints from customers," said the spokesman, who gave only his surname, Tang. "Then we called the police and now they are investigating."

Media reports said the ad offered baby boys for 28,000 yuan ($3,500) and girls for 13,000 yuan ($1,600), reflecting the traditional Chinese preference for males. It promised to deliver infants within 100 days of birth.

"Our aim is to send good news to the thousands of couples around the country who are unable to have children," the site was quoted as saying by the Shanghai Morning Post. The newspaper said it learned of the ad from a reader.

A Shanghai police spokeswoman said she had no information on the case and suggested it was being handled by a district bureau. However, no such case had been registered in Shanghai's Huangpu district, where the site has its offices, said an officer who answered the phone at that police station.

Neither officer would give their name, a common practice among Chinese officials.

China has an active black market in babies and young women, who are bought or abducted and sold to couples who want another child, a future bride for a son or a household servant.

Chinese law allows punishments up to death for people who sell infants, along with lesser penalties for buyers and brokers. However, the law doesn't say whether an offer of such a sale alone constitutes a crime.

Tang, the Eachnet spokesman, said the identity of the purported seller was unclear and it wasn't known whether the offer was serious or an attempt at fraud.

"The seller is very strange. They never bought or sold anything on Eachnet before and we really don't know what their real aim is," Tang said.

Shanghai Morning Post said about 50 people visited the ad before it was deleted. It wasn't known if anyone had contacted the seller.

The site's parent, eBay, has a computer program that filters out ads containing key words pointing to illegal transactions, Tang said. However, since the site routinely offers items such as infant clothing, nothing in the ad tripped any alarms, he said.

Eachnet employees also visually check sensitive ads, but it wasn't clear if they had seen the one placed Sunday.

San Jose, California-based eBay Inc. operates auction Web sites in the United States and 25 foreign countries and territories. The company said it had more than 168 million registered users by the end of the third quarter, a jump of 35 percent from last year.

It completed its purchase of Eachnet in 2003. By last year, the site had 4 million registered users trading the equivalent of tens of millions of dollars online.