A cannabis factory discovered in Hatfield contained more than 490 plants, police say.
A 21-year-old man from London was arrested on suspicion of cannabis production and has been released under investigation while enquiries continue.
Two other people are being dealt with as suspected victims of human trafficking.
Police uncovered the cannabis factory in Errington Close on Thursday after acting on intelligence that the address was being used to sell drugs.
• READ MORE: Hatfield police raid uncovers cannabis factory and suspected human trafficking
Detective Sergeant Christopher Ross said: “We would like to hear from anyone who has any information about this address.
“Cannabis factories use large amounts of water and electricity and these are often syphoned from other people’s supplies and can cause damage or fires to surrounding properties.
“Everyone needs to be alert to these types of factories which can be set up relatively quickly and may only be detectable by those living close by who may notice unusual behaviour by the occupants.”
If you have any information about the supply of drugs, contact Hertfordshire Constabulary via the non-emergency number 101 or report information online at www.herts.police.uk/Report.
Alternatively, you can stay 100 per cent anonymous by contacting the independent charity Crimestoppers on 0800 555 111 or via their untraceable online form at www.crimestoppers-uk.org.
You can look out for the following signs of cannabis being grown in your community:
·A strong and sickly sweet smell
·Lighting and ventilation equipment being taken into the house
·Windows always covered or blocked off
·People coming and going at all hours or neighbours you never see
·Strong and constant lighting at all hours
·High levels of condensation
·Constant buzz of ventilation equipment
·Lots of power cables around the property
A police spokesperson said: “Victims of slavery and exploitation are often hidden in plain sight.
“They are put to work in businesses, homes or other situations where most people would assume their rights are being respected.
“As such it is vital that the public are aware that modern slavery does exist, what signs to look out for and where to report their concerns.”
If you believe a person is a victim of modern slavery or is in immediate danger, call 999 straight away.
To report concerns, get advice, or seek help, call the confidential UK Modern Slavery Helpline at 0800 012 1700 or visit www.modernslaveryhelpline.org/.
Report suspicions of modern slavery by calling 101 or reporting through www.herts.police.uk/.
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