A reward of 50,000 yuan ($8,025) has been offered for information leading to the people who poisoned rare birds on Monday in Tianjin's Beidagang National Nature Reserve.

The management committee in charge of the reserve said that some people intentionally spread pesticides containing organophosphates — which can attack the nervous system of birds — killing 20 oriental white storks and injuring 13 since Nov 11.

Local police is investigating the case.

The management committee decided to offer the reward to help the police and protect the rest of the rare birds in the reserve, it said.