Marriott said the van was white with no windows on its side, a black strip down its side with the letter 'K' in the middle of the black line on both sides of the vehicle.
The driver was described as Maori or Pasifika, believed to be in his mid-thirties. He was wearing a black t- shirt and black cap with white writing. He had a blue and green 'flame' tattoo on the side of his face.
He was described as having a very loud voice and there was no-one else in the vehicle.
Canterbury District Police were taking the matter seriously and urged anyone to get in touch with any information.
"We are issuing the following description of the man and the vehicle in the hope that the public can assist us in our inquiries,"Marriott said.
"If anyone saw a van and driver this morning matching the descriptions given, we need to hear from you."
Police are also appealing for any camera footage held by people in the area, either from security cameras, dashcams, cyclecams, or images from cellphones.
If you can help, please call Christchurch Central Police Station on 03 363 7400 or anonymously on Crimestoppers 0800 555 111.