Last spring, the EU froze the assets of Yanukovych, his two sons and most of his former ministers, with a total of 22 people being accused of misappropriating public funds.
But a senior EU official said that, from a legal point of view, there is an "obvious" problem if Ukraine itself drops the cases against some of the officials -- as it may soon do amid reports that inquiries have ground to a halt.
"So then comes the question of whether we should delist or not delist these people," the official said.
"For some of them there is no more inquiry. For others the inquiry is going on but maybe under other evidence or substantiation."
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The official spoke after a Wall Street Journal report on Thursday quoted diplomats as saying that the EU was likely to drop sanctions on three Ukrainians because the cases against them in Ukraine "have run out of steam."
In May, Yanukovych and his two sons filed suit in European courts against the sanctions, saying the EU lacked a "proper legal basis" for imposing them.
In addition to former Ukrainian officials, the EU has also imposed sanctions on separatist entities and individuals in rebel-held eastern Ukraine.
The EU has long been divided over sanctions on Russia, initially limiting them to individuals after Russia's annexation of Crimea, then broadening them to target the Russian economy after Malaysian Airlines flight MH17 was shot down in July over eastern Ukraine.