German Central Bank has revealed that it has moved 374 metric tons of gold worth more than $15 billion out of vaults in Paris back to Frankfurt over a period of five years.

The central bank also revealed that the final batch of 91 metric tons was moved from Paris back to Frankfurt earlier this year.

The Bundesbank declined to provide details on the means of transfer of gold for security reasons. However, it highly praised the success of the secretive operation.

In a newly released statement, it said, “The bars had been thoroughly and exhaustively tested on arrival in Frankfurt and no irregularities came to light with regard to the authenticity.”

The central bank had been storing 674 tons of gold bars at the Federal Reserve Bank (FRB) in New York and Banque de France in Paris. The plan to return the gold bars to Frankfurt started in 2013.

The lot of nearly 54,000 gold bars, each weighing 27.5lbs with market value of nearly $519,000, will now reside in high-security vaults beneath the central bank’s headquarters in Frankfurt.