Washingotn (CNN) Congressional Democrats are demanding to know who acting Interior Secretary David Bernhardt has met with on the job, seeking to fill holes in what they say are vague calendars.

Like his predecessor, Ryan Zinke, Bernhardt's calendar has described his appointments in vague terms, such as "external meeting" or "call," but leaving out other parties.

The letter, sent Thursday from House Natural Resources chairman Raul Grijalva, suggests the highly limited disclosures make it difficult to determine whether or not Bernhardt has indeed steered clear of meetings he is prohibited from attending under ethics rules.

More than 150 entries from August 2017 through September 2018 "failed to include either a description of the meeting topic or the non-DOI attendees," the letter says, including 98 entries described as "External Meeting."

Since his confirmation as deputy secretary in July 2017, Bernhardt has spearheaded some of the department's most controversial work, including an expansion of oil drilling projects on public lands. On Monday, President Donald Trump announced he would nominate Bernhardt for the secretary job, which also requires Senate confirmation.

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