TOKYO (AP) — Japan’s government has approved a revision to its 30-to-40-year plan to decommission the Fukushima nuclear plant, delaying by two more years the removal of radioactive fuel rods in two of the three reactors damaged in the 2011 disaster.

The cleanup plan so far has succeeding in decreasing the amount of contaminated water and using remote-controlled robots to obtain a limited view of melted fuel debris. Still, the exact location and condition of the melted fuel in the reactors are largely unknown.

The revisions approved Tuesday still plan for the melted fuel to be removed starting in 2021, citing recent findings on more efficient methods.

But the plan lacks details about the duration of fuel removal and final waste storage, raising doubts if the cleanup can be completed within 40 years.