Google's search results display an apparent racial bias, a researcher has claimed.
Harvard professor Latanya Sweeney said that "significant discrimination" was shown when searching for different names on the website.
She claimed that searching for names generally used within black families more often showed adverts aimed at people who had recently been arrested.
Names like Kareem and Keisha showed up advertisements asking "Arrested?" which lead to services to help users search criminal record archives.
Sweeney said these names showed up the links 25% more often.
Meanwhile searches for so-called "white" names were less likely to turn up adverts with criminal record checks.
There was just a 1% chance that her findings were a result of chance and not intentional, she said.
But she also admitted that knowing exactly why the discrepancy existed was impossible without knowing the internal workings of Google's AdSense product. She added it was possible the results were adapting to what links users looking for certain keywords click on.
As a result, it is possible that the bias was caused by unconscious bias by large numbers of people - or a specific choice by advertisers.
Meanwhile Google has denied carrying out "racial profiling" and said it was up to advertisers to pick the words their ads would show up against.
It told the BBC: "We also have an 'anti' and violence policy which states that we will not allow ads that advocate against an organisation, person or group of people."
"It is up to individual advertisers to decide which keywords they want to choose to trigger their ads."