Hungarian authorities confirmed the case was referred to Eurojust, an EU agency based in The Hague that supports judicial cooperation in criminal matters affecting more than one member state.
Hungarian officials did not go into detail about the Netherlands investigation of the captain, 64, who has been with Viking River Cruises for more than a decade.
Not in command during earlier collision
A Viking River Cruises statement provided to Dutch media said the captain was not in command when Viking Idun and Chemical Marketer collided April 1. Viking did not state his actual role.
According to one report, he was on duty as first officer. It is not uncommon for riverboat captains to work on relief duties as first officers.
Death toll rises to 19 in Budapest incident
Meanwhile, Hungarian authorities continue to investigate the cause of the collision between Viking Sigyn and the local excursion vessel Hableány. With 19 people dead, this makes it one of the worst shipping incidents in Hungary's history. All the dead were aboard Hableány.
Nine people, including one of the tour boat's two crew members, are still missing but presumed dead. Officials believe bodies will be found inside Hableány, whose salvage has been hampered by strong current and high winds. A floating crane is standing by, and it is hoped operations could commence over the weekend or early next week.
The Danube's strong current may have carried bodies a great distance. One of the victims was found about 100 kilometres downstream from Budapest last week.
Earlier accident on the Scheldt
The April collision occurred near Terneuzen in the province of Zeeland while Viking Idun, carrying 171 passengers and 44 crew, was underway from Antwerp to Ghent. Five people aboard Viking Idun sustained minor injuries, including four passengers who were treated on site.
The impact of the collision caused significant damage to part of Viking Idun's interior, which was repaired during a stop at Terneuzen before the vessel continued on its itinerary.