As we mentioned last year, the rhea can sprint at 40 mph and, if provoked, deliver a nasty kick capable of seriously injuring a human.
"We are warning local people and particularly those with small children to be on their guard and not to approach the bird, which poses a very real threat to the public due to its size, aggressive nature and the unfamiliar surroundings it could find itself in," Inspector Paul Peatfield of the Nottinghamshire Police was quoted by the Mail as saying.
"Officers are working with the owner to trace the bird as we look to bring his incident to a safe conclusion," he said.
David Lindo, described as a bird expert by the BBC, says rheas are "quite stealthy and they'll be running off, hiding into the bushes ... they can melt into the countryside quite easily."
However, he said that the danger the birds pose has been "overrated."