The police in Xiangyang, Hubei province, said on Thursday that they had found some obstetricians at Xiangyang Jianqiao Hospital were involved in the forgery and sale of birth certificates for at least five babies that were used to register for household residence permits.

The birth certificates mean a baby of unknown origin can be smoothly registered legally at a local public security station by its "parents".

It was the exposure of a volunteer dedicated to fighting human trafficking earlier this week that prompted the Xiangyang police to act quickly. The volunteer posted on social media clandestine audio and video recordings of his communications with some human traffickers and the medical workers of the hospital about their "deals".

These clearly indicated the doctors of the obstetrics department of the hospital, who were involved in the case, were not only well aware of the criminal nature of their behavior but more importantly the crucial role they played in the dirty business.

It is the ease with which the doctors can fatten their wallets in a short time that has tempted them to break the law, despite being tortured by their conscience and professional ethics as the recordings show. As veteran obstetricians, they are in better positions to know the lifelong pain losing a baby can cause to parents and other family members.

The volunteer said he had spent about one year winning the trust of the human traffickers who introduced him to their "acquaintances "working in the hospital in Xiangyang to "buy" birth certificates. The obstetrics department of the hospital is entitled to issue the birth certificates for newborns in it as long as the antenatal care and birth records of the baby are complete, which are crucial to identifying the biological parents and confirming the identity of the baby. That means the forging of the birth certificates entails fabricating a whole set of these documents to whitewash the identity of the babies.

As such it would be difficult, if not impossible, for a local public security station to find the birth certificates are fake, because the certificates are actually obtained through legal means.

The courage of the volunteer deserves credit. But given the national campaign that has been carried out every few years over the past decades to fight human trafficking, a telling sign of the scale of the business, the doctors in the Xiangyang hospital cannot be the only few bad apples in the basket. The case should also serve to remind the police that the campaigns should not only put the human traffickers in the cross-hair but also those that benefit from the deals behind the scene.