Former America Online executive Eric Keller is set to emerge as a key figure in the US government's fraud case against property website Homestore.com after three key executives at the company pleaded guilty.

The investigators, who are building a case against Homestore.com for inflating revenues by £29.5m in the past year, are concentrating their attention on an advertising deal the company made with AOL.

The investigation is running in parallel with a similar probe into AOL's accounting practices around the time of its multibillion-pound merger with Time Warner.

The media giant has already admitted £31m worth of transactions were improperly accounted for.

Homestore.com executives are expected to testify that AOL played an active role in helping their company structure complicated "round trip" transactions, which the government alleges were shams, according to the Wall Street Journal.

Of the three Homestore.com executives - including the former chief operating officer, John Giesecke - who pleaded guilty to fraud, two are understood to have had knowledge of the deal with AOL.

Investigators will now turn their attention to the former Homestore.com vice president, Peter Tafeen, who is understood to have dealt directly with Mr Keller to structure the deals under scrutiny.

AOL insists the transactions are properly accounted for on its own books.

However, insiders suggest AOL executives knew some of the money the company was supposedly receiving from advertisers actually came from Homestore.com.