Store workers were threatened by men who took cash in an early hours raid.
The incident happened at the One Stop store in St Alban's Road, St Annes just before 7am on Monday.
Two men entered the store and made threats to staff, demanding cash.
Police have not said whether any weapons were involved or how much cash was taken.
Lancashire Police was unable to confirm whether the raiders had waited for staff to arrive to open up the store.
Anyone with information should call police on 101.