Web giant Google has revealed to the Information Commissioner’s Office that it still has some of the data collected from home WiFi networks by its StreetView cars in its possession.

The company was supposed to have deleted the data after the ICO’s first investigation of the incident, back in November 2010. Only last month, it reiterated the claim that all the data had been deleted.

But in a letter to the ICO today, Google revealed that it "still has in its possession a small portion of payload data collected by our Street View vehicles in the UK".

Google made the discovery during an internal review of how it handled the disks that contained the payload data – which included emails, passwords and Internet history details of UK residents.

It now wants to delete the data, and is awaiting the ICO’s instructions. The ICO has asked Google to keep the data secure until it has conducted an investigation.

The news is yet another twist in the long saga of Google’s StreetView WiFi data collection. It was first reported that Google was collecting payload data in 2010, prompting a number of national data protection authorities to confront the company.

Google said that the payload data collection had been the work of a single rogue engineer. After its investigation, the ICO requested that Google delete the payload data relating to UK citizens, which it said that it did.

Earlier this year, however, a report from the US Federal Communications Commission claimed that many Google employees had been aware of the snooping functionality. This prompted the ICO to reopen its investigation.

Despite the FFC’s report, Google maintains that no employees besides the rogue engineer were aware of the WiFi snooping.