Two men are thought to have sexually assaulted a woman in a village near St Albans.
Officers from Hertfordshire Constabulary are investigating an attack which took place at around 1.30am on Sunday, June 19.
According to police, the victim - a woman in her 30s - was walking through Marford Playing Fields in Marford Road when she was approached by two males.
They are reported to have sexually assaulted the woman before running off in the direction of the River Lea.
Both men are described as being slim, having Irish accents, and wearing dark clothing.
One is described as being around 5ft 9in tall, while the other reportedly had something covering his face - potentially a bandana.
Specialist police officers are supporting the victim.
Detective Chief Inspector Sam Khanna said: "We are still piecing together what happened but in the meantime I urge the public to stay vigilant.
"I know this news will be alarming but please be assured we are working around the clock to find those responsible.
"We would like to hear from witnesses and those with information about what happened. Any information, no matter how small it might seem, could be vital.
"If you were driving in the area around the time of the incident and have a dash cam, please check it and get in contact if you spot something that might help."
Witnesses and anybody with information can file a report online (www.herts.police.uk/Report) or by phone on 101, quoting crime reference 41/48575/22.
Alternatively, anonymous reports can be submitted to CrimeStoppers on 0800 555 111.
A police spokesperson added: "Anyone in Hertfordshire who has experienced sexual abuse or sexual violence can contact the Herts Sexual Assault Referral Centre (SARC) for practical and emotional support.
"The centre can arrange face-to-face support, sexual health referrals, and provide forensic medical examinations for those who want them.
"This service is open to everyone – men, women and young people, no matter how long ago the abuse occurred.
"To contact Herts SARC, call the 24/7 helpline on 0808 178 4448, email Herts.SARC@nhs.net or visit www.hertssarc.org."
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