The National Park Service is investigating why the Washington Monument would have gone dark Sunday night.

“The exterior lights of the Washington Monument are currently out,” the Park Service tweeted Sunday night. “We are investigating and will have them restored as soon as possible.” The agency has not yet reported why the lights would have gone out.

All of the monument’s external lights were out except for the red lights at its top that are there as a warning to aircraft, reports Fox News.

The outage sparked speculation on social media from several Twitter users.

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One posted a GIF from the 1980 movie “Airplane!” showing a character pulling a plug, and others commented how “super creepy” and how “strange” it was that the monument had gone dark.

Read more at NEWSMAX.