WASHINGTON — The Trump administration on Monday imposed sanctions on 271 employees of the Syrian government agency it said was responsible for producing chemical weapons and ballistic missiles, an effort to impose a sweeping punishment after a sarin attack on civilians this month.

The sanctions on members of President Bashar al-Assad’s Scientific Studies and Research Center more than doubles the number of Syrian individuals and entities whose property has been blocked by the United States and who are barred from financial transactions with American people or companies.

Steven Mnuchin, the secretary of the Treasury, described it as one of the largest actions his department’s Office of Foreign Assets Control had ever undertaken. It seeks to punish those behind this month’s chemical weapons attack in Khan Sheikhoun and previous ones carried out by Mr. Assad’s government, and to deter others contemplating similar actions.

“The United States is sending a strong message with this action that we will not tolerate the use of chemical weapons by any actor, and we intend to hold the Assad regime accountable for its unacceptable behavior,” Mr. Mnuchin told reporters at the White House. “The Treasury Department, together with the Department of State and our international partners, will continue to relentlessly pursue and shut down the financial networks of any individuals involved with Syria’s production or use of chemical weapons.”