Authorities have drained a lake in southern Germany to search for a turtle, after an eight-year-old boy's ankle was bitten while he was swimming last week.

More than 50 firefighters and volunteers are searching the mud and grass around the lake, which is situated in Irsee, about 100 kilometres east of Munich. A special canine unit has also been deployed.

Irsee Mayor Andreas Lieb spoke with co-host Laura Lynch on CBC Radio's As it Happens from the turtle hunt site, where he said that experts have deemed the bite marks to be that of an alligator snapping turtle, a species not native to the region.

Lieb said that the boy's Achilles tendon was cut through twice, and the risk of another attack has made the search urgent.

"That means the turtle is so dangerous," said Lieb. "We have to find it, otherwise it could get to another lake."

Found almost exclusively in the southern U.S., alligator snapping turtles are among the largest freshwater turtles in the world, with some known to weigh over 100 kilograms.

Authorities believe that a pet owner must have released the turtle into the lake, a notion that outrages locals.

"We the people of Irsee, are annoyed by whoever has done all of this because this here is one of our nicest lakes for swimming," Guenther Oberweiler told Reuters Monday. "I think that it is simply grotty and irresponsible of whoever did this," he added.

The turtle, now nicknamed "Lotti," is now featured in warning signs plastered around the lake. Lieb has said he would pay €1,000 ($1,370) to the person who finds the turtle.

"I just offered a reward to somebody who can tell us where the turtle is sitting in the lake," Lieb told Lynch, but he has also warned locals that the turtle can be dangerous.

Irsee folk are afraid that the popular summer spot might never be the same for families if Lotti is not found.

Oberweiler’s wife, Gisela, told Reuters her children would be too afraid to swim in the lake again. "My children would no longer want to come themselves because they will be scared about what could happen," she said.

On the bright side, Lieb said that the injured boy is now doing well, and has even written a text asking the mayor not to kill the turtle, but rather take it to a zoo. The boy also wrote that he wants to become a natural scientist when he grows up, the mayor said.

All of Irsee is now taken up with the turtle hunt. Lieb said that the local bakery is offering turtle bread, and a graffiti champion would be painting a turtle on a town wall.

Experts from Munich are expected to arrive Tuesday to help with the search. Meanwhile, the lake will be fenced off to prevent further incidents, while Lotti could be sinking deeper into the mud, as turtles are known to do.