Authorities arrested a 35-year-old Turkish-German man and his 34-year-old Turkish wife in the raid overnight in the town of Oberursel, near Frankfurt. The couple had been under surveillance.
"According to our current information we have prevented an attack," said Stefan Mueller, the chief of police for western Hesse state.
Authorities in Germany have long warned that the country is at high risk of a terror attack after being identified as a target by extremists, including some who have joined the Islamic State group.
"Of course we talked about the Boston attack last night," said Mueller, explaining why security officials decided to go ahead with the raid. The race "is a soft target, and of course since the Boston Marathon it's part of the security assessment for every marathon in Germany, and of course this is true for cycling races too."
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A part of the Eschborn to Frankfurt race, which will draw around 200 professional riders, winds through Oberursel.
In the Boston Marathon attack, three people were killed and more than 260 injured when two bombs exploded at the finish line on April 15, 2013.
Prosecutors in Frankfurt launched an investigation against the couple in mid-April after an employee at a hardware store informed police about a suspiciously large purchase of a chemical that can be used to make bombs. The couple had used a false name but police were able to identify them and put them under surveillance.
"The result of the raid shows that our suspicions were confirmed," Schreiber said.