The victim was treated at Hawke's Bay Hospital overnight Wednesday before being flown to Palmerston North last night.
KFC general manager Brent Kitto said the incident was of serious concern for the restaurant.
"KFC is concerned that one of their customers was involved in a serious incident outside their Hastings store," he said.
"The police have been into the store to interview witnesses and KFC staff will provide any assistance they can with the police enquiries."
Mr Parker said descriptions of the offenders were not yet known, as investigations hinged on witnesses coming forward with information.
"We still need to talk to more witnesses in relation to that, and there are quite a few more," he said. "The information we have is that the restaurant was pretty busy at the time and also a number of people were in the carpark."
A scene examination looking for DNA evidence including blood and footprints was completed this morning, Mr Parker said. "We are also awaiting CCTV footage which I would say is going to form a major part of the enquiry."
The Mid Central District Health Board were unable to provide a condition update for the victim last night.
Contact Detective Parker at the Hastings police station on (06) 873 0500 or provide information anonymously through Crimestoppers on 0800 555 111.