"There has been fatality at a level crossing at Neustadt am Rubenberge," police spokeswoman Martina Stern told AFP. "He threw himself under a train and died of his injuries. It was definitely suicide."
Jörg Neblung, a close friend and advisor to the six-times capped goalkeeper for the German national football team, said he took his own life.
"I can confirm that it was suicide," he said. "A press conference in Hannover on Wednesday will reveal more details."
The 32-year-old Germany and Hannover 96 goalkeeper leaves a widow and a daughter of eight months, whom they adopted in May three years after their two-year-old daughter died of a heart illness. Enke himself had been suffering recently from a mysterious intestinal sickness.
He pulled out of the Germany squad two days ahead of their 4-0 World Cup qualifying victory over Azerbaijan in early September. However, recently he had professed himself delighted to have returned to training last month.
"It has been a long time, almost a quarter of the season. However, once I resumed training I felt really well," said Enke, who played his last match for the club in Sunday's 2-2 draw with Hamburg.
His death left those closest to him both personally and professionally in total shock.
"We're in shock. I don't know what to say," said national team manager Oliver Bierhoff.
He and national team coach Joachim Löw informed Enke's international team mates - who are preparing for a friendly with Chile this weekend, of the tragedy.
His club president Martin Kind was left stunned. "It is a total catastrophe. I am finding it hard to understand," said Kind.
Later hundreds of the club's fans and several of his fellow players gathered outside the club's offices as a mark of respect with some laying down bouquets of flowers and lighting candles.
Enke was understudy to then first-team 'keeper Jens Lehmann during the 2008 European championships and had been in line to fill his boots before being taken ill in September and October. During that time his rival Rene Adler increased his chances of taking over the role in the national team who have qualified for the 2010 World Cup finals.
Enke had also at one time been linked with a move to German giants Bayern Munich where the former German Under-21 international Michael Rensing had not impressed in his first season between the posts.
However, Uli Hoeness, Bayern's general manager, had made clear they were not interested in paying the €10 million transfer fee.
Several people had advised Enke, who had previously had spells at Benfica, Barcelona and Tenerife, to leave Hannover for a more prestigious club and one that was playing in European club competition so he would improve his chances of becoming German number one.