Mr Friend said traffic was disrupted for about an hour as fire services and council workers tended to the spill, which had spread to Te Rapa Rd.
He said the motorist responsible for the diesel spill had not been identified.
Meanwhile, a teenager who died after his car slid across the centreline and collided with another car on State Highway 4 just south of Tikitiki Rd in the King Country on Saturday morning is yet to be named.
The 18-year-old male driver lost control of his car on a 75 km/h bend in wet conditions about 12km east of Piopio. He died at the scene.
The female driver of the other car was taken to Te Kuiti Hospital with minor injuries.
Police have urged motorists to moderate their speed in wet conditions and be extra vigilant in the busy traffic period leading up to Christmas.
The driver's death takes the Waikato road toll to 51 this year.
Te Kuiti police and the serious crash unit are continuing with the investigation.