At least seven courthouses around Germany, including the Federal Constitutional Court in Karlsruhe, Germany's highest court, said on Wednesday they had received envelopes containing a suspicious powder.

It remained unclear if the substance received at all locations was dangerous. However, officials investigating one case in Eisleben (Saxony-Anhalt) have since ruled out any danger, saying the powder had turned out to be mere sugar.

Employees at the courthouses in the cities of Coburg (Bavaria), Erfurt and Gera (Thuringia), Chemnitz (Saxony), Ludwigslust (Mecklenburg-Western Pommerania) also said they had received similar envelopes in the post.

All locations were evacuated to allow special forces to remove the substance and clean the rooms.

The Federal Criminal Police Office (BKA) said it was investing prospective links between the various cases, while an official in Coburg said authorities in the affected states were in close contact.

According to Saxony's state police, who posted a link to a press report on Twitter, the Chemnitz courthouse reported discovering the powder at around 9:45 a.m. local time (0845 UTC). The police said that no one was hurt and the envelope had been moved to a secure location where it was being examined.

In Gera, in eastern Germany, two employees who came into direct contact with the powder were taken to the hospital, though police say they were likely unharmed. Firemen wearing protective suits were seen carrying the substance out of one of the buildings, which was temporarily closed to the public.

Searches were also conducted in Ludwigslust and Coburg, where employees who came into contact with the substance also underwent medical examinations. Police said they were also likely unhurt.

blc, dm/ksb (AFP, dpa)