Further evidence has been discovered to suggest beavers are being illegally released into the wild in Scotland.
Damaged trees have been recorded in Perthshire, Angus and Fife, and it is thought the animals could be to blame.
Plans to officially reintroduce beavers into Argyll are being considered - but conditions have to be controlled.
Last year an illegal beaver was caught in Perthshire. The punishment for the crime is up to two years in jail or a £40,000 fine.
The beavers have apparently been released near Forfar in Angus and near Aberfeldy in Perthshire.
Gnawed trees have also discovered in Fife - although it has not yet been confirmed that beavers are to blame.
The exact locations of the animals cannot be released because attempts are under way to catch them.
Martin Gaywood, from Scottish Natural Heritage (SNH), told BBC Scotland that the beavers would find it tough to survive.
"They live in these family groups in the wild," he said.
"Once the youngsters reach about two years of age they leave their family groups and go off to look for mates.
"I suspect what may be happening with these two individuals in Tayside is that they are by themselves, spring is in the air, they might be looking for mates which they're never going to find.
"So there is a bit of a sad case here of some lonely beavers looking for mates."
There are international guidelines which must be followed when any animal is being reintroduced.
They include, checking the animal, assessing the habitat and finding out local people's feelings on the idea.
PC Douglas Ogilvie, from Tayside Police, is convinced the beavers have been deliberately released, rather than escaped from a collection.
He said: "If they've escaped they've come a long way, we don't know of any collections in this area.
"There are lots of people out there who'd love to see beavers in the wild, but they have to be released under certain conditions.
"We have absolutely no idea what species this beaver is - it could be American it could be European.
"And there are also certain diseases which beavers can carry, so we must capture the beaver to find out if it's clean and got no diseases."