WASHINGTON — Democratic members of the Senate Homeland Security Committee have asked the Trump administration to explain how it vetted retired Army Lt. Gen. Michael Flynn before he was offered the job of national security adviser.

In a March 1 letter, the four senators asked specifically whether Flynn had been subjected to a lie detector test, which is a routine feature of government security clearance, and whether he had acknowledged receiving money from a Russian television outlet that is owned by the Russian government.

The letter gave the Trump administration until March 17 to respond. The White House has yet to answer, and the senators are expected to renew their request in a second letter this week.

“Now that we know the FBI is investigating Russia’s possible ties to President Trump’s team, we need detailed answers about the vetting of General Flynn and other White House advisers because it’s critical to our national security,” one of the signers, Sen. Jon Tester, D-Mont., said in a statement. “The administration must address these concerns thoroughly in order to prevent future attacks and to keep our nation safe.”

President Trump fired Flynn in February just 24 days into his administration after The Washington Post revealed that Flynn had been recorded conversing with Russian Ambassador Sergey Kislyak.

The firing came two weeks after the Justice Department had told the White House that the transcript of that conversation conflicted with what Flynn had told Vice President Mike Pence about his talks with Kislyak.

Since Flynn’s firing, it’s also been learned that he accepted more than $50,000 from entities with links to the Russian government and that he also was paid $530,000 by a Turkish company to do work that likely benefited the Turkish government.

Flynn’s Russia contacts are especially sensitive because his last role in government was as head of the Defense Intelligence Agency, one of the 16 agencies that along with the CIA and the National Security Agency make up the nation’s intelligence community.

“Russia’s attack on our democracy was a deliberate attempt to undermine the trust Americans have in our government,” Tester said in his statement.