John Ewing/Portland Press Herald

As CNET reported Friday, it looks very much like Google has been building a floating data center made from shipping containers on a barge in the middle of San Francisco Bay. But it may not be the only one of its kind.

Google has not responded to multiple requests for comment. But the project in San Francisco Bay appears likely to be the manifestation of a 2009 patent for a "water-based data center," and would likely leverage the fact that wave energy can provide cheap and plentiful power.

Now it seems as though Google may well have built a sister version of the project, and, according to the Portland Press Herald, it recently showed up in the harbor in Portland, Maine.

In both cases, the structures on both barges appear to be made from a number of shipping containers, many of which have small slats for windows, and each has one container that slants down to ground level at a 45-degree angle.

Tom Bell/Portland Press Herald

If that wasn't enough to establish that the two are related, it's also clear that both were built on barges owned by the same company. The one in San Francisco Bay was built on top of a barge with the registration "BAL 0010," while the one in Portland harbor is on a barge with the registration "BAL 0011." According to online documents, both are owned by By and Large, LLC. That company, which has a miniscule online profile, is also the current tenant in Hangar 3, an immense building alongside the pier where the San Francisco Bay project is under construction.

James Martin/CNET

Now the question is, if there's one in San Francisco Bay and another in Maine, are there more out there? If you've seen a barge with a large structure that looks like the ones pictured here, please let me know.