BRUSSELS, Belgium (AP) -- EU nations agreed Friday to impose strict controls on imports of seafood from Brazil because of what they said were serious health concerns.

Consignments of Brazilian seafood will have to be tested and certified to be clear of high levels of histamine, a potentially harmful chemical which can develop naturally in poorly stored fish. Brazilian seafood arriving in the EU without the correct certification will be tested at the border at the operators' cost.

The EU said a visit by its experts in June triggered concern about "hygiene in the fishery production process and the reliability of the Brazilian approval procedure for fishery establishments."

Tuna is Brazil's main seafood export to the 25-nation EU.

The EU said it was also removing import clearance for five Brazilian fisheries establishments because of hygiene worries.

In a statement, the EU said it was also considering restrictions on other Brazilian food products unless efforts are made quickly to improve hygiene.