Munich police chief Hubertus Andrae said it was unclear whether the suspects are still in the city or even in Germany
German police are hunting for up to seven people suspected of plotting suicide attacks on people celebrating New Year's Eve in the city of Munich.
Some 550 police officers were deployed to hunt down the suspects and secure the city, with authorities warning that the threat remains "high".
A spokesman for German police told the AFP news agency: "We still have many colleagues deployed. There is, as before, a high threat of terror."
The suspects are believed to be Islamic State militants from Syria and Iraq, according to Joachim Herrman, interior minister for the state of Bavaria.
He said German authorities were tipped off by a "friendly intelligence service" - thought to be France - about an apparent attack, which would have been carried out around midnight.
The "concrete tip" indicated the group was planning a massacre involving suicide bombers targeting train stations in the Bavarian capital.
Munich police chief Hubertus Andrae said it was unclear whether the suspects are still in the city or even in Germany.
He told a news conference on Friday: "We received name. We can't say if they are in Munich or in fact in Germany."
Bild newspaper is reporting that authorities have the names of the suspects after a tip-off, thought to be from French security agencies.
Just 90 minutes before the New Year, police evacuated Munich's main rail station and one other terminus in the west of the city.
Mr Andrae said "five to seven" suspects were thought to be involved.
Rail services at both stations were suspended at 10:30pm, with a warning from police urging the public to avoid large crowds.
But many revellers continued their planned celebrations.
Torben Ostermann, a German journalist in Munich, told Sky News: "It's just now 2016 and people are celebrating the New Year like nobody seems to know about the terrorist warning."
He added: "It's a bit weird, though, that we have a terrorist warning and people are firing off their fireworks."
The stations have re-opened this morning, but Munich police are warning people to remain vigilant.
German Interior Minister Thomas de Maiziere said: "The situation in Europe and Germany continues to be serious in the New Year.
"Indeed we did get indications (for a planned attack) yesterday, which were evaluated by the Bavarian intelligence authorities and federal police."
Mr Herrman added there were no concrete indications that an attack could take place imminently and the police presence at the two stations had been scaled back.
European cities have been on high alert over the Christmas period, with both Brussels and Paris cancelling traditional fireworks shows over security fears.
Belgian police have also arrested five people over an alleged New Year plot in Brussels.
Days after attacks in Paris in November, in which 130 people were killed, a football stadium in Hannover was evacuated after a threat was made against a friendly match between Germany and the Netherlands.