Three teenagers were subjected to a knifepoint robbery before the culprits fled through woodland.
Detectives in Huddersfield are appealing for information after the robbery near to TP Woods off Gledholt Bank, in Huddersifeld, between 7.30pm and 8pm yesterday
Two men approached the victims, three males aged 19, and threatened them before demanding money and their mobile phones.
The culprits then fled through the woodland in the direction of Heaton Gardens.
Detective Constable Abbas Hussain, of Kirklees CID, said: "This was an extremely frightening incident for the victims involved and our enquiries are ongoing to trace the suspects.
"I would appeal for anyone who has any information or anyone who saw two males matching the descriptions above to get in touch with police.
"I would also appeal for anyone who witnessed any suspicious activity in the area at the time of the robbery, to contact officers."
The first suspect is described as white, with a tanned complexion, around 14 to 16 -years-old, 5ft 8ins tall, and of slim build. He was wearing a black puffer jacket and dark tracksuit bottoms.
The second suspect is described as white, 5ft 5ins tall and of slim build. He was wearing a navy blue t-shirt, dark jeans with a belt.
Anyone with any information is asked to contact PC Abbas Hussain at Kirklees CID via 101, quoting crime reference 13170341889.
Information can also be passed anonymously to independent charity Crimestoppers on 0800 555 111.