Police in Munich, Germany, cleared two city train stations
An increased police presence continues Friday, despite an announcement from Bavarian Interior Minister Joachim Herrmann that the alert level had been lifted.
But few answers are available about how severe the threat was and who might have planned it.
Here is a list of some of the key facts and questions about the story:
THE THREAT: Officials in the southern state of Bavaria said they received the first alert of a possible threat at about 7:40 pm (1840 GMT), according to Herrmann. He said the warning included information about a concrete time and place for an attack.
Anonymous security sources have said the warning came from France.
Another earlier warning was believed to have come from the United States days before, which cited names of possible suspects and target locations.
THE ALLEGED TERRORISTS: Herrmann said the initial warning clearly identified the planners as between five and seven Iraqi and Syrian nationals with links to the jihadist group Islamic State.
Munich police chief Hubertus Andrae later said that the planned attacks would have involved suicide bombings.
However, Andrae conceded at a press conference on Friday that it was unclear whether the named suspects existed at all as investigators puzzled over their whereabouts.
WHAT HAPPENED: Munich police issued an alert via Twitter around 10:40 pm that there was the danger of an attack. Shortly thereafter, they announced that the main train station, as well as a separate station in the city's Pasing district, about 10 kilometres away, would be shut down.
Police deployed 550 officers as the new year began.
The train stations reopened between 3:30 and 4 am on Friday. However, police remain on high alert, with a noticeably higher police presence on the streets. A search for the suspects continues.