An apparent security flaw on the Shanghai police website has led to a huge leak of private information about informants and people making complaints to the department.
The leaked files included their names, home addresses, phone numbers and the letters they sent to the police chief's e-mail address, according to a review by the South China Morning Post.
The bulk of the files, dated from August to yesterday, were emails and photographic proof of alleged wrongdoing - some implicating police officers.
The data could be publicly accessed on a server that hosts the Shanghai Public Security Bureau's website from Friday afternoon, and perhaps earlier, to yesterday afternoon. The server became unavailable after that.
The bureau could not be reached for comment. The cause of the leak is unclear.
Complainants contacted about the leak expressed shock. "How could they do this to us?" said a man from the Minhang district of the city who lodged a complaint earlier this year.
He said the bureau did not respond to his letter. "I hope the authorities can treat our reports more seriously by ensuring the informants are protected from such exposure," he said.
The e-mail complaint system, run by the police department handling petitions, allows citizens to air grievances and to report crimes, the website stated.
The force has encouraged tipsters to provide their personal information so their cases can be handled in a "timely manner". It promised that all personal information would be protected.
A woman who accused policemen of beating up her family members said she was disappointed by the breach of security.
"To disclose our information is like telling those police officers that I'm the whistleblower," she said. "I did my job, but apparently the police didn't do theirs."
Police said they received and responded to nearly 1,300 complaint e-mails in the first two months of the year.