A second six-member team arrived on Saturday to take over from Tolba's team.
The IAEA last week confirmed the shutdown of North Korea's sole known functioning reactor at Yongbyon, the first concrete progress after numerous negotiations involving the US and other regional powers.
Unfinished work
The nuclear inspectors are also working to verify the status of two unfinished reactors – a spent fuel reprocessing facility and a fuel fabrication plant.
The North fired a test nuclear weapon in October. Four months later, Pyongyang agreed to scrap its nuclear programme in exchange for economic and political concessions in a deal with the US, Russia, China, Japan and South Korea.
It has been promised one million tonnes of fuel oil in exchange for disabling its nuclear facilities under the six-party agreement struck in February last year.
South Korea has sent 50,000 tonnes of oil to the North as compensation for shutting down Yongbyon.