The first element of the Fehmarn Belt Tunnel between Germany and Denmark could be lowered off the Danish island of Lolland as early as this spring, Danish state-owned construction company Sund & Bælt said on Thursday.

A special vessel that is to sink the tunnel elements has been approved by the Danish Maritime Authority, the company said.

The ship's task was "complex, so numerous tests were necessary," deputy contract director Lasse Vester said in the statement. "Now we have received approval for the ship and can start lowering it."

The construction consortium Femern Link Contractors (FLC) can now begin the necessary preparations, it said.

In January, Sund & Bælt said the opening of the 18-kilometre tunnel was likely to be delayed until 2031, partly because of missing permits. Once the first tunnel elements have been sunk, a new timetable will be drawn up, it had now said.

Huge infrastructure project

According to Sund & Bælt, the Fehmarnbelt Tunnel for cars and trains is one of Europe's largest infrastructure projects. It will eventually connect the German island of Fehmarn with the Danish island of Lolland.

On the German side, a hinterland connection is being built that also includes the Fehmarn Sound Tunnel between the island and the German mainland.