Want the latest climate news in your inbox? You can sign up here to receive Climate Fwd:, our new email newsletter.

WASHINGTON — The Environmental Protection Agency had a total of 33 threat investigations underway as of mid-March — 10 of them involving Scott Pruitt from the last six months — a security assessment released Monday shows, offering the most detailed tally yet of threats against the agency’s top official.

The memos, provided to The New York Times in response to a Freedom of Information request, are the documentation that Mr. Pruitt has pointed to in justifying the round-the-clock security he has received since taking over the agency in February 2017, as well as first-class flights he has taken, among other unusual security expenses.

The memos also show the degree to which Mr. Pruitt is not the first E.P.A. administrator or agency employee to receive threats. The total number of threat investigations by the agency has fluctuated from 47 in fiscal year 2015 to 43 in 2016 to 50 in 2017, most of which was during the Trump administration.