Police have advised dog walkers to keep their pets on a lead in a forest in case they are poisoned.
Dorset Police said a dead buzzard was found in the Ashmore area of Dorset, though its cause of death is yet to be determined.
The poisoning of three white-tailed eagles was also investigated by police earlier this year.
A police spokesperson said a new multi-agency investigation is expected to take place. People are asked to contact police on 101 if they find other dead animals in the area and to take a photograph, but not to touch them.
Source: BBC