WASHINGTON — President Barack Obama's aides sent text messages to tens of thousands of people about crowd control, public transportation and even the weather today as he took the oath of office and immediately started building another massive technology-based list of supporters.

Starting a week before Obama took office, aides to the inaugural committee warned visitors of subway stations' closures, television schedules and even train schedules — part of Obama's aggressive communications strategy that delivered him his Democratic Party's nomination and later the White House. The same minds also immediately swapped the White House's Web site at 12:01 p.m. EST, even before Obama had delivered his inaugural address to a nation changed by his Internet-savvy political campaign.

"President Obama started his career as a community organizer on the South Side of Chicago, where he saw firsthand what people can do when they come together for a common cause," blogged Macon Phillips, the White House's director of new media, just moments after Obama became the nation's 44th president.

"Citizen participation will be a priority for the administration, and the Internet will play an important role in that."

Phillips was also the director of the campaign's tech effort that announced Joe Biden as the pick for vice president and the inaugural committee's effort that sent brief messages to cell phones during a day when all of Washington was buried under a crush of visitors and security.

"If you are still in transit to the Mall, we suggest you head west of 14th Street," aides advised this morning as officials coped with crowds heading toward the inauguration ceremonies on the west steps of the Capitol.

As Biden took his oath of office, guests' pockets buzzed and chirped with a note about a closed subway stop near the National Mall. And as Obama's family left the platform, aides urged careful exits for guests: "Please stay and watch the parade on the jumbotrons. Encourage your neighbors to exit the Mall slowly."

As a million visitors made their way toward Obama's noontime inauguration, aides worked with local officials, Washington Metro officials and military aides to send quick messages to the phones.

It was the latest move from Obama's technology team to connect with supporters.

Just minutes after taking office and stewardship of the White House Web site, Obama started to build another list — this time using official government resources — to keep people updated about his administration's efforts. His advisers see that list — and his 13 million person political list — as ways to harness public sentiment to outflank troublesome opponents, news organizations and rival interest groups.

It's a relationship Obama's aides are determined to sustain; even before Obama delivered it, aides posted his inaugural address on the new White House's blog.

"WhiteHouse.gov is just the beginning of the new administration's efforts to expand and deepen this online engagement," Phillips said.