THREE people were arrested overnight on suspicion of attempting to break in to Dudley Zoo.
Officers were sent to the scene after a 999 call was received from a member of the public who had seen a group scaling a perimeter wall at around 12:50am.
The police helicopter was also deployed over the 40-acre site.
A 22-year-old woman and two men, aged 24 and 26, were arrested on suspicion of attempted burglary.
No animals were hurt during the break-in.
A spokesman from Dudley Zoo said: "A neighbour alerted our security team who in turn contacted the police. The site has been fully checked and there are no signs of damage or access to enclosures."