A man in his 30s was threatened, put in a van and covered in "a bleach-like substance" near Harpenden.
At around 4pm on Thursday, January 4, the man received a work call to recover a car that had broken down on Coles Lane, underneath the M1 bridge between Harpenden and Markyate.
When the man arrived at the scene, he was met by a woman inside a grey Toyota.
Two to three men, who were described as wearing bike helmets, then emerged and threatened him before putting him in a van.
A "bleach-like substance" was then thrown over the victim, who was driven to an unknown location.
He was later returned to Coles Lane, at around 6pm, where he ran to a nearby address in Birch Grove and phoned the police.
He later attended hospital to be checked over.
Detective constable Sophie Mansell said: "This was a distressing incident for the victim who continues to be supported by officers at this time.
“I understand that news of this incident is likely to cause concern among the local community, and our investigation is continuing at pace as we work around the clock to try and trace the suspects.
“We believe that this was a targeted attack and that there is no wider threat to the public.
“As part of our investigation, detectives have been assessing CCTV opportunities, conducting house-to-house enquiries and utilising other police tactics.
“We are still encouraging anyone with information to please get in touch with us.
"Were you in the area the time of the incident and saw what happened, or have any further information that may assist our investigation?
"Also, if you were driving in or around Coles Lane at the time of the incident and have a dash cam fitted, please check it as you may have recorded some crucial footage.
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“Please email me at Sophie.Mansell@herts.police.uk with any information, no matter how small or insignificant you think the details you have may be. Thank you.”
Information can also be reported to Hertfordshire police online at www.herts.police.uk/ro/report or by calling the police's non-emergency number 101, quoting crime reference 41/1019/24.
Anonymous information can be given by contacting Crimestoppers on 0800 555 111 or via crimestoppers-uk.org.
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