Was it wrong for the US Department of Homeland Security to push Twitter to reveal the identity of a user critical of President Donald Trump?

That's what the department's inspector general, John Roth, says his agency will try to find out.

Roth sent a letter (PDF) Friday to Oregon Sen. Ron Wyden saying the department is conducting an internal investigation into whether a demand sent to Twitter in March by the Bureau of Customs and Border Protection "was improper in any way."

The bureau, part of Homeland Security, wanted to know who was behind the Twitter account @ALT_uscis. USCIS is the acronym for United States Citizenship and Immigration Services, also part of Homeland Security. The "ALT" account attacked Trump over his immigration policies.

Wyden asked for a probe on April 11 over concerns about free speech. In his letter to Wyden, Roth said his department is committed to honoring the First Amendment.

"We strive to ensure that our work does not have a chilling effect on individuals' free speech rights," Roth wrote.

Wyden's office posted the letter online. It comes two weeks after Homeland Security dropped its demand when Twitter sued the government agency. Twitter argued that those behind anti-Trump accounts, some admitting they work for the government, risk harassment and retaliation -- and maybe their jobs -- if their identities are revealed.

The social network accused the government of violating the First Amendment and political speech rights. The @ALT_uscis account was created around the time Trump issued a January order restricting immigration, which was later blocked by courts.

Twitter also said in its suit that the demand and any laws behind it don't apply to its users. Such a demand is typically issued in cases where Customs finds something suspicious with merchandise being imported.

Roth and customs officials didn't respond to a request for comment. A Twitter spokeswoman declined to comment.

Here's the full letter: