(CNN) Russia may have significantly modernized a nuclear weapons storage bunker in Kaliningrad, a sensitive exclave of Russian territory sandwiched between Poland and the Baltics, as tensions between Russia and the West continue to rise, according to a new report.

On Monday, the Federation of American Scientists (FAS) published aerial photographs that the group says show the facility in the Baltic outpost has been under major renovation since 2016.

FAS said the images document refurbishments at the site back in 2016, when one of three underground bunkers at the location was excavated and deepened before it appeared to have been covered over in recent months, "presumably to return (to) operational status soon."

A satellite image from the Federation of American Scientists that apparently shows a buried nuclear weapons storage bunker in the Kaliningrad region, which the group says has been under major renovation since mid-2016.

Hans M. Kristensen, the director of the nuclear information project at FAS, said in a blog post that it was unclear from the images if any nuclear weapons had ever been or will be kept at the facility.

"The features of the site suggest it could potentially serve Russian Air Force or Navy dual-capable forces. But it could also be a joint site, potentially servicing nuclear warheads for both Air Force, Navy, Army, air-defense, and coastal defense forces in the region," Kristensen wrote.