AMSTERDAM (AP) -- A Dutch historical museum got more than the bronze swords, golden helmets and precious gems it bargained for when it organized an exhibition on ancient treasures from Ukraine: it also inherited a diplomatic mess.
Russia annexed the Crimean Peninsula a month after the Allard Pierson museum opened the "Crimea -- Gold and secrets of the Black Sea" exhibition in February. Curators say now they are not sure where to return the objects on display when it ends in August.
Officials from both Ukraine and Russia insist the Crimean treasures must be returned to them.
"We're investigating who the legal owner is," said museum spokeswoman Amber van Schagen-Fayein Friday.
The museum has enlisted experts from the University of Amsterdam and the Dutch Foreign Ministry for advice on what to do now.
Among the most stunning objects in the exhibition are a solid gold Scythian helmet from the 4th century B.C. and a golden neck ornament from the second century A.D. that weigh more than a kilogram (two pounds) each.
Ukraine's Foreign Ministry asked the Dutch ambassador in Kiev last week to guarantee the safe return of the collection to Ukraine.
The country's culture minister Evhen Nishchuk said it was his office that approved the exhibition in the first place -- in one of the largest releases of the country's historical collections abroad ever authorized -- and it must return via the same route.
"This is about the national security of the cultural heritage of the Ukrainian state," Nishchuk said in a statement.
But four of the five museums that contributed artifacts are located in Crimea.
Somewhat poignantly, a major theme of the exhibition is the region's history of frequent conquests and as a crossroads for different peoples and cultures: modern Sevastapol was once the site of a Greek colony that traded grain for pottery from the Athenian Empire.
In the grave of a noblewoman who lived on Crimea's west coast in the first century A.D., archaeologists recovered an Egyptian scarab, Roman pots from Italy and France, and a Han dynasty lacquer box thought to have come from China via the Silk Road.
Russian President Vladimir Putin's culture envoy Mikhail Shvydkoi said the treasures must be returned to Crimea -- but he acknowledged the situation is awkward.
"Since Crimea became part of another country, we have got a legal issue here but we're going to find a solution for it," Shvydkoi said.
The exhibition was put together by one of the most prominent archaeologists of the region, Valentina Mordvintseva. In the exhibition documents, she is listed as based at the Ukrainian National Academy of Sciences in Simferopol, Crimea.
Associated Press reporter Nataliya Vasilyeva contributed to this story from Moscow.
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.