Saudi Arabia is nearly completing the construction of its first nuclear reactor, Bloomberg reported.

According to the source, satellite photos show vessel at reactor site in Riyadh.

Arms control experts are alarmed, as Saudi Arabia has not yet joined the international system of rules that other nuclear powers adhere to in order to ensure that civilian atomic programs are not used to create weapons.

“There’s a very high probability these images show the country’s first nuclear facility,” said Robert Kelley, a former IAEA director who also led the U.S. Department of Energy’s remote sensing laboratory. “It means that Saudi Arabia has to get its safeguards in order.”

According to Saudi Arabia’s energy ministry, the facility’s purpose is to “engage in strictly peaceful scientific, research, educational and training activities in full compliance with international agreements.”

The Kingdom has signed all international non-proliferation treaties, the ministry said, stating that the facility is open to visitors.

While Saudi Arabia openly declares its ambitions to build a nuclear power plant, little is known about the types of monitoring that the kingdom intends to bring into action. An increasing number of arms control experts are scrutinizing Saudi Arabian nuclear work because of official statements that the kingdom might try to acquire nuclear weapons.

Crown Prince Mohammed bin Salman announced last year that the kingdom would develop a bomb if regional rival Iran made it. These statements caused alarm in the community of nuclear observers, as they have more opportunities to access nuclear facilities in Iran than in Saudi Arabia.

“The much louder debate in Washington is about whether Saudi Arabia acquires nuclear weapons,” said Sharon Squassoni, a researcher and former diplomat on non-proliferation issues at George Washington University.

Attention to the program has been increased after the US Congress launched an investigation into the allegedly illegal transfer of sensitive technologies to the kingdom.