Image copyright
YappApp
A security guard was doused in liquid and threatened with a lighter during a robbery at an Asda shop in Leeds.
A group of armed robbers wielding an axe and a sawn-off shotgun stole money being delivered to a cash machine at the store, in Killingbeck Drive, at about 07:00 BST.
The suspects fled in a white van later found on fire in a nearby cemetery.
Police said they are not able to say what the liquid thrown at the guard was until it can be tested.
A force spokesman added: "The threat was not seen through and he was not injured."
Det Insp Al Burns, of West Yorkshire Police, said: "This was a really frightening experience for the staff involved.
"Although no-one was physically injured, they have been left very badly shaken by what happened."
He added officers were treating the robbery "very seriously" and carrying out "extensive inquiries to establish the full circumstances and to identify those responsible".
Armed police have been seen outside the store as investigations continue.
It is not believed to be linked to an armed robbery at a post office in Leeds on 3 September.
Police want to hear from any witnesses, particularly those with mobile phone or dashcam footage.
Follow BBC Yorkshire on Facebook, Twitter and Instagram. Send your story ideas to yorkslincs.news@bbc.co.uk.