A 19-year-old man remained in hospital today in a stable condition with wounds received in a fight involving a knife at the McDonald's Restaurant in Napier.

A second young male was treated and discharged after the two were taken to Hawke's Bay Hospital separately following the incident.

One of the young men crashed through a plate-glass window which shattered across the forecourt and tables at the front of the building off Thackeray St, a short distance from the Napier CIB.

Detective Sergeant Daren Pritchard, of Hawke's Bay CIB, told Hawke's Bay Today it was thought just the two were involved in the fight which happened in the dine-in area of the restaurant about 9pm.

One was "known" to police previously, the other was not, he said.

Police are reviewing CCTV footage and seeking witnesses, many of whom fled the restaurant.

The dining area and counter were closed as police investigated, while staff dealt with increased traffic at the drive-through.

At least one weapon was recovered. "No, it wasn't a plastic knife," said Mr Pritchard.  

The restaurant is staffed mainly by young people, family of whom expressed concern on a facebook thread, which included parents worried about the traumatic effect on teenagers and children who witnessed the violence.

One commented her daughter had been there, and was so traumatised she didn't want to go back.

"Poor girl," another responded. "She has to live with that. Nobody deserves to see that crap."

It was business as usual at the restaurant today, with the window replaced.