Prosecutors in the Netherlands said Friday they have opened a criminal investigation into seven Dutch companies and their directors for allegedly breaching European Union sanctions against Moscow, by helping Russia build a bridge to Crimea.

The companies involved are alleged to have supplied machines, machine parts and other services for the construction of the 19-kilometer long bridge spanning the Strait of Kerch, the prosecutor's office said.

This represented a violation of sanctions imposed by the European Union after the annexation of the Crimean peninsula by Russia in 2014, the prosecutors said, as they explicitly ruled out the sale of machines and related services for use in Crimea. "This is a serious offense, undermining the EU sanction regime," the prosecutors said in a statement.

Individuals found to have breached sanctions can be sentenced to up to six years in prison or a maximum fine of 82,000 euros ($97,818), a spokeswoman for the prosecutor's office said, while companies can be fined up to 820,000 euros.

The prosecutors did not name the companies involved, but said the transactions under investigation took place between November 2015 and the latter part of 2017. The spokeswoman declined to give any further details.