"After a short pursuit both cars were stopped and the offenders apprehended," he said.
Both cars were returned to their owners undamaged.
One male and one female appeared in the Hamilton Youth Court yesterday in connection with the thefts, while an older female appeared in the District Court yesterday.
A fourth female will appear in the District Court next week.
Mr O'Brien said he had concerns to raise with the parents of the four teenagers.
"While it was pretty good to be able to return the first victim's car to her relatively unscathed we have some concerns we want to raise with the parents of the four teenagers around their access to alcohol and supervision," he said.
He advised drivers to avoid leaving their cars unlocked with the keys in it.
"Our message around valuables in cars, and the vehicles themselves, is lock them or lose them."