Police in Hastings are awaiting the results of a blood test before considering whether to charge a bus driver with drink-driving.
The bus travelling between Napier and Hastings was stopped by police on Monday afternoon after passengers who had been on a previous trip expressed concerns about the driver's behaviour.
The driver of the Go Bus was taken to the Hastings police station, where a breath-alcohol test showed him to be over the legal limit.
A police officer with an appropriate licence completed the route.
The driver's bus licence has been suspended, pending the result of the blood test.
Go Bus says it is the first incident of this type. Commercial director Craig Worth says the company recently introduced a drug and alcohol policy for its 750 employees and has an extremely rigorous recruitment process.