Milton Mount playgroup in Pound Hill, Crawley, has been closed with immediate effect after a member of the public found the toddler wandering alone.
A spokesman for Sussex Police said: “Police were called at 2.50pm on Tuesday (May 12) by a woman who had found a three-year-old girl wandering around in Milton Mount, Pound Hill, Crawley.
“Officers attended and went to Milton Mount playgroup which was very closeby and explained that a child had been found on her own nearby. The playgroup staff then checked and realised the girl was missing.
“The girl was brought back to the playgroup and reunited with her grandmother who had arrived to collect her. She was not hurt. The staff and the girl were spoken to and she told police she climbed over a 3ft fence to get out. The incident has been recorded.”
A spokesman for the playgroup said: “It is with much regret that Milton Mount playgroup will be closed with immediate effect due to an ongoing investigation.
“Please understand that the safety of all children at the playgroup is of paramount importance and we will be working with OFSTED and the Local Area designated officer to address and correct any concerns.
“A vigorous internal investigation will be held along with a review of procedures and staff training to ensure that the playgroup can reopen as soon as possible.”