North Korea seems to have reopened its Yongbyon plutonium plant, the International Atomic Energy Agency (IAEA) said Monday.

“There are indications the reprocessing plant at Yongbyon has been reactivated,” an IAEA spokesman said, according to Reuters. “It is possible that it is reprocessing spent fuel.”

The reactor was shut down in July 2007 but government authorities in the capital Pyongyang said in September 2015 that the plant was operational again. They added that the plant was working on improving the “quality and quantity” of its nuclear weapons.

The IAEA's access to the country was cut off in 2009 and the UN nuclear watchdog relies on satellite data to monitor its activities.

At a news conference during a quarterly IAEA board of governors meeting, IAEA chief Yukiya Amano said that recent satellite images show “activities related to the five-megawatt reactor, expansion of enrichment facilities and activities related to reprocessing."

Experts reportedly say that the reactor is capable of manufacturing one bomb’s worth of plutonium a year.

Since the plant has been in function, North Korea has conducted multiple missile tests and its fourth nuclear weapon test resulting in the toughest-ever U.N. sanctions against the country.

The amount of weapons-grade uranium and plutonium that the country possesses is unclear. Reports say that the plutonium manufactured at the Yongbyon site is used in North Korea’s nuclear bombs.