Update at 11:41 a.m. ET (by Brett Molina): USA TODAY's Jon Swartz has more details on the latest on the Skype outage and the brief down time for Twitter.

Update at 8:23 a.m. ET (by Brett Molina): Skype says millions of users appear to be signing into Skype with no problems, but engineers are still working to bring the Internet phone service back to normal.

"Unfortunately, it's not possible for us to predict on an individual level when you'll be able to sign in again, and we thank you for your patience in the meantime," says Skype's Peter Parkes on their official blog.

Update at 1:50 a.m. ET ( posted by Nancy Blair): Skype appears to be back up for at least some users, according to reports on Twitter and our own tests, although there is no official word on the Skype blog.

On Twitter, @Skype posted this:

Thanks for your continued patience while we get everyone back online – sorry especially to those of you who are still waiting.

Original post:

Internet phone company Skype says its popular service is down. It is investigating the cause of the outage, which could affect millions of consumers.

"Our engineers and site operations team are working non-stop to get things back to normal," reads an update on Skype's Twitter feed.

MID-DAY UPDATE WEDNESDAY: Skype just released the following statement: "Earlier today, we noticed that the number of people online on Skype was falling, which wasn't typical or expected, so we began to investigate.

"Skype isn't a network like a conventional phone or IM network -- instead, it relies on millions of individual connections between computers and phones to keep things up and running. Some of these computers are what we call 'supernodes' -- they act a bit like phone directories for Skype. If you want to talk to someone, and your Skype app can't find them immediately (for example, because they're connecting from a different location or from a different device), your computer or phone will first try to find a supernode to figure out how to reach them.

"Under normal circumstances, there are a large number of supernodes available. Unfortunately, today, many of them were taken offline by a problem affecting some versions of Skype. As Skype relies on being able to maintain contact with supernodes, it may appear offline for some of you.

"What are we doing to help? Our engineers are creating new 'mega-supernodes' as fast as they can, which should gradually return things to normal. This may take a few hours, and we sincerely apologize for the disruption to your conversations. Some features, like group video calling, may take longer to return to normal.

"Stay tuned to @skype on Twitter for the latest updates on the situation – and many thanks for your continued patience in the meantime."

By Jon Swartz