Knifepoint robbery at woman's house in Bradford
Police said it happened after the 27-year-old woman answered a knock on the door at around 2.15am today (Saturday) at her home on Southfield Lane, Bradford.
The masked male suspects forced their way in and one threatened her with a knife while the others searched a downstairs room.
They fled empty handed after a witness called the police.
A West Yorkshire Police spokesperson said: "Nothing was taken in the incident which left the victim unhurt but very distressed. One of the men was described as black, while the other three were wearing masks."
Anyone who saw four men near the house before the robbery happened is urged to come forward.
Detective Inspector Sally Shipley, of Bradford District CID, said: “This was clearly a very frightening experience for the victim and we are conducting a number of enquiries today to determine a motive for what took place.
“Neighbourhood Policing officers are conducting reassurance patrols in the area and officers are also conducting door to door and CCTV enquiries.
“We would like to speak with anyone who may have information or who saw four men entering and leaving the property or hanging around outside just before the incident took place.
Witnesses should call Bradford CID on 101 referencing crime number 13180423103.