A gang of masked men broke into a house and threatened the occupants with a stun gun.
The four men, all wearing balaclavas, entered the house on York Street in Church at around 5.30pm on Sunday, February 10.
Detectives said they threatened the two males who were inside the home before making off with a wallet containing around £20 in cash.
Police said the motive of the attack was unknown and expressed concerns about the gang being armed with a taser.
Detective Inspector Jill Johnston, of Lancashire police, said: "Police enquiries are under way including CCTV and forensic examinations and house-to-house calls.
“No one has been injured. Because there is a stun gun or something similar to a stun gun that's of concern to the police.
“Anyone with information or who may have seen a Golf or Astra type dark car driving away in the direction of Lion Street can contact us on 101."