A crash site where two Auckland teenagers were killed is causing problems for police due to vandals.

Police told Stuff that a group of suspected teenagers have trashed the building where Ella Berrington, 13, and Nathan Quist, 17, were killed last month.

Ella was a Year 9 student at Pakuranga, while Nathan was a student at Tāmaki College.

The pair were killed when their car slammed into a building on Pakuranga Rd about 4.30am on July 20.

They were found dead in the crashed car about three hours later. Police said speed was a factor and it was later found that the car had been reported stolen.

The car had veered off Pakuranga Rd and crashed into a building near Udys Rd and Johns Lane.

The building contains a number of businesses, including a dentist's practice.

Since the incident, Sergeant Ben Thornton told Stuff that teenagers had been gathering at the crash scene most nights and vandalised the property.

In the last 10 days, two fires had been lit under the building and the fire service had to be called, mud had been thrown on windows and a nearby office was broken into and laptops were stolen, among other items, Stuff reported.

Tributes and messages have also been scrawled on the walls underneath the building.

Thornton said the anti-social behaviour was upsetting local business owners and needed to stop.

"The business owners at the crash scene have been very understanding and have allowed the grieving process – they've been patient and respectful and let youth gather down there," Thornton told Stuff.

"[They] don't deserve to have their building trashed. We will make arrests if necessary. Kids cannot abuse the trust of the business."