The RSPCA is investigating how vulnerable and frightened lambs came to be dumped in people's gardens.
The animal welfare charity said the latest incident, in Scruton Avenue, Sunderland, is the third in recent weeks.
On May 16 a resident wake up to find a shivering lamb in their front garden. It still had its umbilical chord attached and was much too young to be away from its mother.
The RSPCA said there are no farms in the local area and the garden is enclosed so the lamb could not have wandered in.
A similar case had been reported to Northumbria Police three days earlier in nearby Forbes Terrace when the distressed lamb was head-butting the garden fence in an attempt to get out.
The RSPCA said social media reports indicated there had been an earlier incident in the same area, adding that the supposed practical jokes are putting lambs at risk.
Rescue officer Heather Wade said: "These little ones were only days old so were very vulnerable and would have been frightened to be away from their mum.
"I know the lambs could not have wandered into the gardens as they were enclosed, so it suggests someone has deliberately done this and I have no idea why - maybe they think it is some kind of joke.
"We are not sure where they have come from as there are no nearby farms so we could not reunite them with their mum and they are now being hand-reared by a specialist."
Anyone with information is asked to call the RSPCA on 0300 123 8018.