An unknown number of falsely installed screw anchors could keep the Biblis nuclear power plant offline for some time.

"We'll get Block B operating again only when we're sure that everything is okay," said a spokesman for the plant.

Essen-based RWE, the operator of the plant, said that around 4,000 special screw anchors would require closer inspection before the plant would be up and running again. The screw anchors are used to fasten down pipelines in both Block A and Block B of the plant to make them "earthquake-safe."

Block B was closed on Monday after the falsely installed screw anchors were discovered in Block A. Hesse's Environment Ministry then decided that all the anchors in both blocks should be examined, which is not possible when the plant is in operation. Block A had already been taken off-line on September 15 for a general overhaul.

Inspections of all the anchor screws could take several weeks.

As part of the planned closure of nuclear power plants in Germany, Biblis A was to be put out of commission in the coming year, Biblis B in 2009. RWE had, however, submitted a formal request to extend the use of reactor Biblis A longer than planned.

Nuclear power plant closure

Ruling parties continue to argue over the gradual closure of nuclear power stations, which a government led by the center-left Social Democrats agreed on with utility companies in 2000.

Chancellor Angela Merkel's conservatives (CDU/CSU) and the Social Democrats (SPD) compose the ruling grand coalition. Last year, when the coalition was formed, the SPD vowed it would stick to the deal of nuclear power plant closure, while the conservatives aim to reverse it to cap power prices.

Nuclear power generation currently supplies a third of German electricity.