A man has been arrested after an unknown substance was sprayed in the face of Post Office staff.
The incident took place at around 5.30pm yesterday (Friday, May 10).
A man went into the Post Office in Abbey Street, Accrington, and sprayed a number of people in the face with the substance, the contents of which are not currently known.
Three members of staff and one member of the public were injured.
Police, fire and ambulance attended the scene and the injured parties were treated.
The man demanded staff open the shop's safe before making off with cash on a pushbike.
Since the incident a 33-year-old man from Accrington has been arrested on suspicion of robbery.
He remains in custody.
Anyone with any information about the incident can call police on 101 quoting incident reference 1057 of May 10.
Alternatively call independent charity Crimestoppers on 0800 555 111.