(in full) BRUSSELS (Reuters) - Belgian prosecutors said on Thursday they had detained a man of Iraqi nationality after a series of letters containing a nerve gas ingredient were sent to the prime minister's office and the U.S. and British embassies.

A spokeswoman for the federal prosecutor's office told a news conference the 45-year-old man was arrested late on Wednesday in the western Belgian town of Deinze.

Two postal workers were taken to hospital after being exposed to the chemicals in the letters at mail depots.

No one else was hurt by the 10 letters sent to a variety of targets, including a court trying al Qaeda suspects in Brussels, the Saudi Arabian embassy, three ministries, an airport and a port authority. The letters were received on Wednesday.

The brownish-yellow powder contained phenarsazine chloride, an arsenic derivative used in nerve gas, as well as hydrazine, an agent used as a rocket propellant, the Health Ministry said. Both substances are also found in pesticides.

The letters contained no more than a spoonful of the chemicals -- not enough to be life-threatening -- but caused irritation to the eyes, skin and breathing.

The prosecutor's office spokesman said that if the man was found guilty of injuring the people and making them unable to work, he could face between six months and two years in jail.

A spokeswoman for the federal police said that five police officers had also been taken to hospital on Thursday, but she could not confirm a report on Belgian radio that the officers had been affected by powder from the letters.

Belgian news agency Belga said the policemen had been working at an office block in central Brussels housing various judicial services, which had then been evacuated for fear the powder could spread through the air conditioning system.