Several people posted on social media that the assaulted person may have been hit in the head with a brick or concrete block and that this may have occurred on the premises of a nearby rest home, although police would not confirm details.
A St John's Ambulance spokeswoman confirmed they had received a call at 12.14pm on Monday and attended an incident on Mako Mako Rd.
She said one patient in a "moderate condition" had been taken to Palmerston North Hospital.
A spokesperson at Millvale House rest home, just across the street from the dairy on Mark Mako Rd, said the incident had not involved any of their staff or residents.
She said she understood the incident to have involved a member of the public, but could not comment further.
A staff member at the dairy spoken to by the Horowhenua Chronicle confirmed the incident had involved the shop and said "everyone is okay".
Police confirmed two people have been taken into custody and will be referred to Youth Aid, with inquiries ongoing.
The Mako Mako Rd dairy was also robbed in February.
Shortly after that incident, a 17 year-old male was charged with aggravated robbery, demands with intent to kill, failing to stop and dangerous driving after he allegedly fled the scene, was pursued by police and crashed his car near Hokio Beach.