James Martin/CNET

The mystery surrounding a large structure built on a barge docked in San Francisco bay is deepening. Is it a floating Google data center? A floating Google Glass store? Or something else altogether?

On Friday, I reported exclusively that a company, very likely Google, has set up shop on Treasure Island, located between San Francisco and Oakland, and has been building a large structure made from shipping, or cargo, containers on a barge. Some evidence suggests it might be a floating data center, including the fact that Google itself has a patent for such a concept.

Google has not responded to multiple requests for comment.

John Ewing/Portland Press Herald

The Portland (Maine) Press Herald also ran a story recently about a structure on a barge showing up there, and photographs taken by the newspaper look similar to what is being built in the San Francisco Bay. Plus, the barge being used in San Francisco and the barge in Maine are both owned by the same company, By and Large, which is leasing a large hangar adjacent to the Treasure Island pier on which the San Francisco barge is docked. I found that Tim Brandon, who was said by the Treasure Island Development Authority to be tied to By and Large, was also tied directly to Google.

Now, a report from KPIX -- the San Francisco CBS affiliate -- suggests that the Treasure Island project may not be a floating data center at all. Rather, KPIX -- owned by CNET parent CBS -- reported that the project is going to be a floating Google Glass store, and that the plan might be to tow it into San Francisco's Fort Mason for some indeterminate time.

James Martin/CNET

KPIX reported that Google has been unable to acquire the permits needed to bring it to San Francisco. The TV station was told that the San Francisco Bay Conservation and Development Commission has been unwilling to grant the permit. A CNET request for comment from the same commission last week was not returned.

The idea of a floating Glass store is an odd one, but anything is possible from Google. In fact, after our story ran on Friday, I was contacted by someone who said he had knowledge that the project in the works is a Google store of some kind. The tipster, who is well-connected in Silicon Valley but asked to remain anonymous, told me that he had heard from multiple sources at Google that the company plans to float the Glass stores from city to city by rivers, and that the idea for the project came straight from either Larry Page or Sergey Brin, Google's founders. Finally, he said, the idea is in part that Google wants to launch stores without looking like they are trying to chase Apple.

If Google is working on building intentionally non-Apple style stores -- usually open and filled with natural light -- it's possible Google is going after an entirely different retail experience by making structures out of dozens of narrow shipping containers with few windows.

But one expert in the custom cargo container business thinks that the structure in San Francisco Bay -- at least as it looked like in pictures he was shown -- couldn't be used to hold a lot of people. To have a store, said Joel Egan, the principal at Cargotecture, you'd need big open spaces, and a building made from the "little cubbies" that are inside shipping containers doesn't seem practical. Plus, Egan said, there would need to be lots of exits, something that doesn't appear to the case on the structure in San Francisco Bay, or the one in Maine. "I would say no, it doesn't [look appropriate for a store]," Egan said. "It would be a lame store. That doesn't sound right."

In addition, an independent marine engineer told me he was involved in a project to build a large-scale Google backup data storage center a few years ago -- about the same time Google received its patent. Upon seeing my original story on Friday, this engineer told me that he thought that the project was exactly the one he'd been working on for a while but that he figured went dark. The engineer asked for anonymity because of concerns about breaking confidentiality agreements with Google.

Google was "looking at putting together a data center, or really...a backup center, in case of some kind of natural disaster," the engineer told me. "They'd have all their data from the region backed up at this center. This could easily tow it with a tug out of the area, and be able to easily bring it back in and get it up and running while facilities would be down in the area. And...the master plan at the time was to build upwards of a dozen of these things. About four in the States, and then have them worldwide, over in Asia, Europe, South America. They were planning on putting in a lot of these things worldwide."

That the project in San Francisco Bay might be part of that master plan, he said, was bolstered by the existence of the Maine project.

The engineer further went on to say that Google had initially wanted to build these backup centers on retrofitted ships and even went so far as to buy one. But eventually, he and others involved in the project convinced Google that tearing down and configuring the ship would be far more expensive than building from scratch. As a result, he said, they persuaded Google to buy brand-new barges and build on top of them.

After my story suggesting Google might be building a floating data center ran, the engineer said, "I saw that and said, 'I know what that is. My God, I haven't heard anything about this in years. So they are finally building this thing.'"

Of course, since he worked with Google, plenty has changed and Google could have changed course entirely. At that point, Google had yet to invent Google Glass.

Daniel Terdiman/CNET

Whatever this mystery structure atop the barge in San Francisco turns out to be, one thing no one seems to doubt at this point is that Google is involved. If not, why would this yacht, which sure looks like Page's personal boat, Senses, have been docked last week alongside the very pier on which the project is being built?