The investigation reveals that the 43- year-old man of the western city of Bochum had left several people seriously injured after causing the attack.
A German police spokeswoman said the suspect is in police custody and is expected to be brought before the judge on suspicion of attempted murder.
German police investigations believed that the 30-year-old man who sat at a table outside the café was the intended target of the attack. He was hit with the most acid and suffered serious injuries.
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A woman sitting at the same table and a waitress working nearby were also victims of the acid attack. Two other guests who witnessed the incident suffered shock, while the paramedics were also injured after coming into contact with the potent acid.
According to the police, as many as 14 people were injured in the attack. However, a police spokesman reported that the customers had been drinking coffee and eating cake "in a very relaxed manner" shortly before the attack.
The suspect was arrested nearby shortly afterwards. Police homicide detectives searched his apartment in the town of Bergkamen, around 32 kilometres away, on Monday night.
Investigators have remained tight-lipped about the motive and background to the attack.
Authorities are still conducting tests to determine the exact substance used in the attack.
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