Parents have been warned about a man who has been acting suspiciously in Heath Lane Nursery School's car park, Hemel Hempstead.
Police were called at 8.51am on Wednesday, January 16, after a man followed a parent from Hemel Hempstead town centre to the nursery.
The man then allegedly spent time in the nursery's lower car park, standing around with 'no reason to be there'.
School staff searched the grounds but the man was not found.
Health Lane Nursery sent email alerts to parents, and warned other nurseries in the area about the man.
Staff said: "Several parents have been very alarmed by his behaviour.
"The incident has been reported to the police".
The man is described as Asian, wearing black trousers and a beige/green coloured top, with a beanie/woolly hat. He is approximately 5ft 11in tall.
The Safer Neighbourhood Team are conducting enquiries into the incident.
If you witness any suspicious activity or have any information, please contact Hertfordshire Constabulary via the non-emergency number 101, quoting ISR 142 of January 16.