Three men have been hurt including a man shot and another stabbed at a party at Abbots Langley, near the Warner Brothers Studio Tours Complex.
Emergency services were called to reports of a large-scale disturbance in High Elms Lane at around 9pm yesterday (Sunday night).
Three men sustained their injuries during the incident and were taken to hospital.
One of the men has since been released.
Four people are currently in police custody in connection with the incident.
The road remains closed today while investigations continue. CCTV enquiries are continuing and witnesses are being spoken to.
Police say "Anyone with information about what happened is asked to contact police on the non-emergency number 101.
Detective Inspector Justine Jenkins from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit said: 'I fully understand that this may cause concern in the local community but I would like to reassure people we are doing all we can to establish exactly what has happened. At this stage it is believed to be an isolated incident between parties known to each other, who were attending a private party.
As arrests have been made it is important not to speculate on what has happened so as not to prejudice any action going forward and I would urge people to be responsible when posting on social media.
Police will remain in the area by way of reassurance. If you have any information about what happened, please call us on 101."
Those attending the crematorium will however be able to gain access by vehicle but please allow more time for your journey.
Students sitting exams will also be able to gain access to schools in the area but otherwise, High Elms Manor, St Michael's Catholic High School and Parmiter Schools will remain shut until further notice.
A police cordon remains in place at either end of the country lane, just off the A405 North Orbital Road.
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