President Donald Trump listens to a question as he meets with reporters on Air Force One while in flight from Andrews Air Force Base, Md., to Palm Beach International Airport, Fla., Thursday, April 6, 2017. Alex Brandon/AP SAN FRANCISCO - Twitter on Friday dropped a lawsuit it had filed a day earlier against the U.S. government, saying in court papers that the government had withdrawn a summons for information about an account critical of President Donald Trump.

A lawyer for the social media company, Mark Flanagan, wrote in court papers that a U.S. Justice Department lawyer told Twitter about the withdrawal of the summons on Friday and that the demand "no longer has any force or effect."

It was not immediately clear why the government had withdrawn the summons or whether it had closed an investigation it said it was conducting. The Justice Department, which defends federal agencies in court, declined to comment. The Department of Homeland Security, which issued the summons, had no immediate comment.

Twitter cited freedom of speech as a basis for not turning over records about the account, @ALT_uscis. The people behind the account have not disclosed their identities, but the use of "ALT" with a government agency acronym has led many to assume government employees are behind such tweets.

A screenshot of the Twitter account the US government was seeking to unmask Twitter

The lawsuit said the account "claims to be" the work of at least one federal immigration employee.

The acronym U.S. CIS refers to U.S. Citizenship and Immigration Services, and the account describes itself as "immigration resistance." Trump has vowed to build a wall along the U.S. border with Mexico and has promised to deport millions of illegal immigrants.

Following Trump's inauguration in January, anonymous Twitter feeds that borrowed the names and logos of more than a dozen U.S. government agencies appeared to challenge the president's views on climate change and other issues. They called themselves "alt" accounts.

A Twitter spokesman declined to comment beyond the court papers.

The lawsuit gave Twitter a chance to assume a favorite role as a defender of free speech, offering a respite for a company that has struggled recently to expand its audience, excite investors or attract new revenue streams.

On Thursday, Senator Ron Wyden, an Oregon Democrat, said in a statement that the summons was a waste of resources to try to uncover an anonymous critic, and he called on the Homeland Security inspector general to investigate who directed the "witch hunt."

How it all started:

When it first filed its lawsuit on Thursday, Twitter said the account in question, @ALT_USCIS, had been known to "express public criticism of the department and the current administration," but that Twitter and its users were protected under the First Amendment.

The US government, Twitter said in the complaint, "may not compel Twitter to disclose information regarding the real identities of these users without first demonstrating that some criminal or civil offense has been committed, that unmasking the users' identity is the least restrictive means for investigating that offense, that the demand for this information is not motivated by a desire to suppress free speech, and that the interests of pursuing that investigation outweigh the important First Amendment rights of Twitter and its users."

Twitter argued that the "defendants have not come close to making any of those showings."

"To unmask an anonymous speaker online, the government must have a strong justification," Twitter said in the complaint. "But in this case, the government has given no reason at all, leading to concerns that it is simply trying to stifle dissent."

(Reporting by David Ingram; Editing by Jonathan Oatis and David Gregorio)