Concerned Harpenden residents alerted police to what they believed to be suspicious behaviour today.

A Herts Police spokeswoman said: “We have been called by two members of the public today regarding three men in a large white double glazing van who were seen looking in gardens and an open garage in Roundwood Lane, Harpenden, at around 11.50am.

“The first report to police was at 12.10pm by a man who said he had challenged the men as he did not believe they were double glazing tradesman.

“The men then left.

“A woman then called at 1.06pm to say she had seen the vehicle in Barnfield Road.

“Enquiries are on-going to locate the vehicle.”