Details are sketchy, but it appears that U2 performed at least one new song during a "secret" event Friday night in Amsterdam. It happened at the Gashouder building at Westergasfabriek, a former gasworks facility that's now used for public events.

The event itself wasn't really a secret, since U2.com advertised it earlier in the week and asked fans in the area to come forward if they wanted to attend. Several Dutch media outlets also spilled the beans as the performance was happening, estimating that 200-300 people were invited inside.

U2 fans outside the venue have been tweeting now that it's over. Here's what we understand happened:

U2 performed at least one new song a handful of times. There are reports that some of the lyrics included lines like "when the lights went down" or "the lights go out." There was a second new song during the performance, but reports suggest U2 didn't play it live. (U2Valencia tweeted it was "by video.") An early report that U2 performed "You're The Best Thing About Me" seems to be incorrect.

And that's about all we know at this point. It sounds very similar to U2's video shoot in Santa Monica, California, for "Invisible" back in January 2014. If you made me bet money on what happened tonight, I'd say U2 was shooting a video for 1-2 of the new tracks on Songs Of Experience -- a good sign that we're getting a new album in 2017, as the band has promised several times recently.

UPDATE: We now understand from fans at the performance that the first song (the one U2 played a handful of times) may be titled "Blackout." That was the only new song planned for the evening. When filming concluded, fans were treated to a second new song over the PA after Bono received permission from Island to do so.