Preparations had been hastily made to flood the tunnel with 14.5 million litres of ground water in order to shore up underground walls which had been poorly built.

This was deemed the only way to ensure the central Heumarkt station site did not collapse by providing counter pressure against the walls which would likely be strained by rising groundwater levels due to spring runoff.

But the plans were shelved on Saturday afternoon after it emerged that ground water levels were not rising as quickly as expected.

“We can delay the flooding without reducing the safety concept which remains complete,”

city official Guido Kahlen said.

The city has been gripped by the drama playing out among its foundations, which started a year ago with the deadly collapse of the historic archive building, after which it was revealed that corners had been cut in metro tunnel construction. In some areas more than 80 percent of the stabilising metal anchors have been found to be missing in tunnel walls.

Falsified records concerning the construction work have been uncovered, with some suggestion that organised crime could have been involved.

Although the flooding action has been called off, the fire brigade remains ready to implement the plans should it become necessary.