A mysterious barge off the coast of San Francisco has captured the nation's curiosity amid speculation that the structure might be a secret facility operated by Google.

The barge, a four-story vessel stacked with shipping containers, resides at Hangar 13 on Treasure Island in the San Francisco Bay. Mirian Saez, director of island operations, told ABC News that the space is being leased by By and Large LLC, but could not confirm whether the company is associated with Google.

But Lawrence Goldzban, executive director of the San Francisco Bay Conservation and Development Commission, said his organization has been in touch with Google about the vessel. He could not, however, offer any information about its intended purpose.

"I have no idea," he said when asked what the structure would be used for.

Google has not responded to ABC News' multiple requests for a comment, but CNET has reported that Google might be building a floating offshore data center. The company did file a patent in 2009 that includes blueprints for a "floating platform-mounted computer data center," according to the patent document.

But KPIX 5, a CBS affiliate in San Francisco, has reported that the barge was constructed to serve as a retail store for the Google Glass product. The station quoted an unnamed source reportedly close to the project, who says that the barge will be moved to nearby Fort Mason to operate as a marketing center for the new device.

But Goldzban of the conservation commission told ABC News that it would be illegal for a vessel to be parked in the bay and used as a permanent store or marketing facility.

"Under the law of California, vessels cannot be moored for long periods of time," he said.

Adding to the intrigue is a report from the Portland (Maine) Press Herald, more than 3,000 miles away, that describes a similar-looking structure in the Portland Harbor. City officials there are equally mum about the owner and purpose of the barge.

The Portland Harbor Commission says it cannot comment. A representative from the U.S. Coast Guard could not provide details about either barge but said it is investigating the matter.

(Photo Credit: KPIX/CBS/ABC News)