"NZ Post will support the driver and their family as they make their recovery."
A St John Ambulance spokeswoman said one ambulance and one rapid response vehicle were sent to the scene, with one patient in a moderate condition transported to Hawke's Bay Hospital.
A Hawke's Bay District Health Board spokeswoman confirmed the man, in his 40s, is now stable.
A spokesman from Cafe at Westermans, on Russell St, Hastings, said several customers who were sitting inside witnessed the incident.
"It was scary by the sounds of it for the driver," they said.
The van was found about 9.30am dumped on Riverslea Rd, Hastings.
Police took two people into custody, charging a 21-year-old man with unlawfully taking a motor vehicle. The other person has not been charged.
The 21-year-old man was due to appear in Hastings District Court on Monday.
An NZ Post spokesperson added: "We are investigating the contents of the van to work out what, if anything, was taken, and will then notify customers if necessary."