It may not be an ecological problem at all if a few got out - they might die and that would be the end of it. But without knowing for certain it's a risk that we should not intentionally take. Prevention is far easier than cleaning up.

As an example, U.S. Farmers lose billions every year because one guy wanted to bring the European Starling to the new world. He released a few dozen in NY's Central Park and now they are estimated to number over 100 million birds across the contiguous 48. The English House Sparrow has a similar story. The selfishness of just a few people can alter an entire nation's ecology forever.