The dead birds have been found in the Somerset Levels, an area of marsh and farmland that drains into the Bristol Channel, the Daily Express reported Friday. The region is an important stop for migrating birds.
This week, a reward of 26,000 pounds ($42,000) was offered for information leading to the killer, including 10,000 pounds donated by Sir Terry Pratchett, the best-selling fantasy and children's book author. Pratchett, who lives in Salisbury about 50 miles east of the Somerset Levels, told the Express the swan killer should receive a "medieval" punishment.
The killings are being investigated by the Royal Society for the Protection of Cruelty to Animals and Avon and Somerset Police.
"It is important people realize that any information or gossip, no matter how small, could be crucial and they come forward to share it," Police Inspector Roger Tolley of Burnham-on-Sea said.
Investigators do not know what the killer's motive might be.
"It's obvious to everyone here that a maniac is responsible for these deaths," said Pauline Kidner, who founded the Secret World Wildlife Rescue Center in East Huntspill, Somerset.