Although the completion of the $4.5 billion sale of Nortel's 6,000 patents has been announced, the U.S. Department of Justice intends to continue scrutiny over the deal. It is reportedly intensifying an investigation into whether the deal would unjustly hobble competitors.

In order to see whether the patent portfolio buyers have any plan on launching lawsuit against competitors, specifically ones using Google's Android mobile operating system (OS), the U.S. Department of Justice is deepening an investigation, WSJ reported.

The deal, which got approval from U.S. and Canadian bankruptcy courts on July 11, was made with a group of technology companies including Apple, EMC, Ericsson, Microsoft, Research In Motion, and Sony. The group, which called itself "Rockstar Bidco" won the action last month against Google, Intel and others. The 6,000 patents and patent applications cover technologies such as wireless, wireless 4G, data networking, optical, voice, Internet, and semiconductors.

Search giant Google placed an initial bid of more than $900 million for the patent portfolio back in April. However, it couldn't snap up the deal after Apple joined hands with other companies.

As per the WSJ report, the Justice Department is interviewing the winning companies, and it can still "impose conditions" on them albeit the deal has already been completed.

Rumors are that the Rockstar Bidco might have individually approved all of the companies to partake in the auction, while it held back the right to "take a fresh look" if it had further concerns. As Apple joined the consortium later, with the final price shoot up, therein lies potential issues, according to sources close to the matter.

The bid was "a sign of companies coming together not to buy new technology, not to buy great engineers or great products, but to buy the legal right to stop other people from innovating," said Kent Walker, Google general counsel.

Google acquires over 1,000 patents from IBM

Meanwhile, Google, whose feeble intellectual property portfolio has made it susceptible to legal attack, has bought some 1,030 patents from IBM in a bid to shield itself from an assault of patent lawsuit.

The newly acquired patents are related to several different markets including "Web-based querying" and "fabrication and architecture of memory and micro processing chips", SEO by the Sea reported. They also include servers and routers. Rumors are rife that Google also has plans over wireless technology company InterDigital's intellectual-property portfolio after the Nortel patent bid loss.