Police searches of two garages used by a terrorist suspect in the western German town of Castrop-Rauxel on Monday failed to uncover any hazardous substances, according to authorities.

"We have found nothing in the end that can be used as evidence," a spokesman for state prosecutors in nearby Düsseldorf said.

The searches came after two Iranian brothers were arrested on suspicion of planning to carry out a terrorist attack with bioweapons.

The brothers, aged 32 and 25, were taken into custody in the Ruhr area town on the weekend for allegedly planning an attack using the toxins cyanide and ricin with the intent of killing "an unspecified number of people,"  prosecutors said.

The two are believed to have been motivated by extremist Islamist ideology.

A police search of the elder brother's apartment on Sunday also failed to uncover any hazardous substances. The garages were also said to be used by him.

The arrests came after tipoffs from US police authorities.

Younger brother already in detention

It has meanwhile emerged that the 25-year-old brother was sentenced to seven years' detention in 2019 for attempted murder.

The conviction came after an incident in July 2018 in which the man threw a large branch weighing around 10 kilograms (roughly 22 pounds) onto a German highway, hitting a car driven by a 32-year-old woman. The driver was injured by shattered glass but survived.

The man was under the influence of alcohol at the time of the incident. The court ordered that he be treated for alcoholism following a period in normal detention.

A spokesman for state prosecutors in Dortmund said the man was still being held at a detoxification clinic in another city in the Ruhr area, Hagen, when he was arrested on the weekend. The spokesman said the suspect had been given weekend leave to stay with family members.

Official calls for better use of internet intelligence

The interior minister of the western state of North Rhine-Westphalia, where Castrop-Rauxel is located, has now called on German authorities to improve their use of the internet in gathering intelligence about possible terrorist attacks.

Herbert Reul, whose job includes overseeing police and security affairs in the state, told German television that "the important thing is to know early on who is planning what."

He said he did not understand why Germany was so reticent about using existing techniques for gleaning intelligence on the internet, while acknowledging that different countries had very different rules governing how they could intercept and investigate online information.

Germany's data protection regulations are among the strictest in the world, something that is often attributed to the fact that two regimes in its history — the Third Reich and communist East Germany — used surveillance of the people to assert control.

What is ricin?

Ricin is a highly potent plant-derived toxin that works by entering the cells of a person’s body and preventing them from making the proteins they need.

It is listed as a biological weapon by both the United Nations and Germany's Robert Koch Institute for disease control and prevention.

The definition of biological and chemical weapons can overlap to an extent because biological weapons can include infectious bacterial or viral agents, or toxins derived from biological material.

The use of such toxins produced by some living organisms is covered under the provisions of both the international Biological Weapons Convention and the Chemical Weapons Convention.

tj/rs (dpa, AFP)

Editor's note: This article was updated to reflect that ricin is listed as a biological weapon by both the United Nations and Germany's Robert Koch Institute for disease control and prevention.

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