Police are looking for a woman they believe gave birth in the bathroom of an Internet cafe yesterday morning and then left the baby dead.

A cleaning woman found the dead baby in the bathroom at the Ruide Online Net cafe in Jing'an District at about 11am yesterday. The bathroom was covered in fresh blood at the time, police said.

She alerted the police immediately and the baby was pronounced dead on the scene by paramedics.

Police blocked the toilet for investigation and didn't reveal the dead baby's gender.

They believe the mother is a woman in her early 20s who spent the night in the Internet bar and was spotted heading to the bathroom on surveillance video.

While the woman had to show her ID card to get online, the cafe's clerk apparently didn't record all of the information, leaving police with only the woman's surname, Shen, to go on.

The cafe was able to confirm that the woman arrived at 11:10 Saturday evening and used a computer until 8:01 yesterday morning when she logged off and paid her bill. She didn't leave at that time however.

Police reviewed the surveillance video and it showed the woman covered her belly with a coat and moving slowly towards the toilet at about 9:50am.

No one else entered the bathroom until the cleaning lady arrived and discovered the dead baby, according to police.

Customers and staff told police they didn't notice anything suspicious about the woman during the night.

"She seemed to be covering her belly with a coat all the time. It's hard to tell whether she was pregnant or not," a cafe worker recalled.

Workers said the woman looked normal when she walked out of the cafe on her own.

"I was too horrified to see if the bloody baby was a boy or girl. I just ran out to call for help," said the female cleaning worker.