BERLIN (AP) — German special police forces arrested a Syrian man in a raid on his apartment Tuesday after receiving intelligence from American officials that he was planning an extremist attack, authorities said.

The 26-year-old “radical Islamist” was planning an attack in Germany designed to “kill and injure a maximum number of people,” federal prosecutors said in a statement.

The Syrian, whose name wasn’t given, came to Germany in 2014 as an asylum seeker and had been living in the country with “protected” status, said Martin Steltner, a spokesman for Berlin state prosecutors.

The suspect had obtained information online on how to build bombs and talked about planning an attack in internet chats, and an “allied foreign intelligence service” provided the information to German authorities, Berlin’s top security official Andreas Geisel told the dpa news agency.

Steltner would not comment on where the tip came from, but a U.S. official speaking on condition of anonymity to discuss the case told The Associated Press it had come from law enforcement and intelligence cooperation between American and German authorities.

U.S. Embassy spokesman Joseph Giordono-Scholz said he could not elaborate.

“We can’t comment on the specifics of this investigation, but we are proud of the longstanding, strong cooperation between United States and German law enforcement agencies,” he said.

Federal prosecutors, who lead most terrorism investigations, said the suspect had been under surveillance for several months, and had started in January procuring material and chemicals, including acetone and hydrogen peroxide, to build an explosive device.

“These were to be set off at an unknown time and place in Germany,” they said.

The man was arrested by GSG-9 police special forces in Berlin’s Schoeneberg district early in the morning.

Geisel said the suspect worked as a cleaner in a Berlin elementary school and at the city’s famous Bode museum.

“We assume that there was a considerable danger,” Geisel said.

German authorities have foiled several attacks by Muslim extremists since a Tunisian man attacked a Berlin Christmas market nearly three years ago killing 12 people.