BERLIN (AP) — German security officials said Thursday they have foiled what could have been an imminent Boston Marathon-style terror attack after raiding the home of a suspected Islamic extremist, seizing a bomb, a firearm, ammunition and chemicals that can be used to make explosives.

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.

Mueller stressed that security officials couldn’t yet confirm whether a professional cycling race scheduled to take place Friday was the target of the attack, and declined to say whether authorities suspect known extremist groups to be involved.

“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.”

A part of the Eschborn to Frankfurt race, which will draw around 200 professional riders, winds through Oberursel. Friday is May Day, a public holiday in Germany and in most European countries, and thousands of spectators usually line the route.

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.

“Suspicions were heightened in recent days by the fact that the accused (man) was observed in the area where tomorrow’s cycling race will take place,” Frankfurt’s chief prosecutor, Albrecht Schreiber, told reporters.

“The result of the raid shows that our suspicions were confirmed,” Schreiber said.

He said investigators found a functioning pipe bomb, 100 rounds of ammunition, parts of an assault rifle and three liters (nearly a gallon) of hydrogen peroxide, a training rocket for an anti-tank weapon and various other chemicals.

Schreiber said the man was linked to the extreme Islamic Salafist movement in the Frankfurt area and was known to police for 15 previous offenses. The two suspects would likely appear before a judge later Thursday, he added.

“I want to emphasize that an attack was prevented, but it will have to be seen whether a concrete attack against tomorrow’s cycle race was planned,” he said.

Mueller, the police chief, said hydrogen peroxide can be used to produce a substance called TATP. It has been used by extremists to build improvised explosive devices in the past, including by the “shoe bomber” Richard Reid, who tried to detonate a bomb in his shoe during a trans-Atlantic flight.