It turned out while moving radioactive waste to a newly-built storage facility during the so-called hot tests on Dec. 31 that the radiation level of the waste was higher than estimated. If the waste were loaded into casks, as planned, a certain reaction could have occurred, the article said.

The new storage facility was built by Nukem Technologies, a German company controlled by Russia's nuclear energy giant Rosatom.

Ina Daukšienė, head of communication at the INPP, confirmed to 15min that the tests had been halted due to "certain problems".

Aurelija Vernickaitė, spokeswoman for the energy minister, said that the tests had revealed "certain shortcomings in the processes".

"As it often happens during such tests, the need for additionally improving the operation of technical equipment was established," she said.

According to 15min, the European Commission and the European Bank for Reconstruction and Development (EBRD), which finances the project, have been notified of the incident.

Sources told the website that this might cause a delay in the project.