The 19 pirate suspects were released because they had not attacked Portuguese property or citizens.
And these pirates had explosives
The Portuguese helicopter chased the pirates back to their "mother ship", or command vessel, and briefly detained about 19 pirates, a Nato spokesman said.
Explosives and grenade launchers were discovered on the mother ship when Portuguese special forces boarded "with no exchange of fire", Lt Cmdr Alexandre Santos Fernandes said.
"It was almost a kilogramme of high explosives. If used correctly it can open a hole in the hull of a ship and sink her," Lt Cmdr Fernandes said.
"It is the first time we have spotted high explosives on board a pirate ship, normally they just stick to AK-47s and RPGs (grenades)."
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