North Korea continued to expand one of its missile plants during the weeks leading up its summit with the U.S. last month, according to an analysis of satellite imagery by researchers in the U.S.

The report, released by the Middlebury Institute of International Studies, concludes that North Korea was expanding its nuclear capabilities despite North Korean leader Kim Jong Un’s claims that the country would denuclearize, Bloomberg reported.

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“The expansion suggests that, despite hopes for denuclearization, Kim Jong Un is committed to increasing North Korea’s stockpile of nuclear-armed missiles,” David Schmerler and Jeffrey Lewis, the report’s authors, wrote.

Kim and Trump signed a joint agreement during the June 12 summit reaffirming North Korea’s commitment to denuclearizing the Korean Peninsula, but critics have noted North Korea often makes this promise without taking action.

The Middlebury Institute report comes on the heels of a conclusion by U.S. intelligence officials that North Korea is planning to hide its nuclear stockpile and production facilities, reported by The Washington Post.

Trump on Sunday said North Korea is “very serious” about denuclearization, but the these reports indicate the opposite.