Janaf's offices were searched by the Office for Suppression of Corruption and Organised Crime (USKOK), state broadcaster HRT reported. The interior ministry confirmed that the investigation is related to suspected economic crime and corruption, but declined to name the arrested, it added.
According to unofficial information, the police operation was prompted by suspicions of favourism in awarding contracts worth over tens of millions of kuna, HRT said.
Janaf's consolidated net profit edged up 1.6% on the year to 149 million kuna ($23 million/20 million euro) in the first half of 2020, with revenue rising 4.6% to 374.7 million kuna, the company has said.
Janaf has terminals on the island of Krk, as well as in Sisak, Virje, Slavonski Brod and Zitnjak, and operates 631 kilometres of pipelines. It has 1.94 million cubic metres of storage capacity for oil and 222,000 cu m of capacity for the storage of petroleum products.
The company's shares traded flat at 4,240 kuna by 15:09 CET on Thursday on the Zagreb bourse.
(1 euro = 7.54029 kuna)