Prosecutors in Washington have dropped felony rioting charges against four of the six journalists arrested while covering Inauguration Day protests, but charges remain in place against two others.

The six were among 230 people arrested during violent demonstrations that took place just blocks from the inauguration of Donald J. Trump, who was sworn in as the 45th president on Jan. 20. Some protesters smashed shop windows in downtown Washington and set a limousine on fire.

Charges against three of the journalists — Matthew Hopard, John Keller and Alexander Rubinstein — were dropped on Monday, according to Bill Miller, a spokesman for the United States attorney’s office for the District of Columbia.

Charges against a fourth — Evan Engel, a writer for the media and technology site Vocativ — were dropped on Friday.

In a series of statements, the attorney’s office said it had determined that the four defendants are, indeed, journalists. But Mr. Miller declined to comment on the charges pending against the remaining two, Shay Horse and Aaron Cantu, or to say whether prosecutors considered them reporters.

“There were 230 people who were charged with felony rioting that day, and to date these are the only case we have dismissed,” Mr. Miller said. The attorney’s office said it was continuing to review evidence related to the arrests.

Advocates for freedom of the press expressed concern about the arrest and prosecution of reporters.

“We remain concerned that Aaron is still being charged with a felony because our understanding is that he was there as a journalist,” Courtney Radsch, the advocacy director of the Committee to Protect Journalists.

“If the authorities have evidence that is not true, they need to present that or else not continue to charge him,” she added. “Journalism is not a criminal activity.”

Mr. Cantu declined to comment on Monday, citing the advice of his lawyer. An attempt to contact Mr. Horse was not successful.

The case against the six journalists was complicated by the fact that all except for Mr. Engel are freelance reporters who do not have a media organization to vouch for them before the authorities, Ms. Radsch said.

“Freelancers often face additional challenges with respect to reporting and safety because they are freelancers,” she said.

That can become an especially sticky situation when a freelancer or blogger blurs the lines between reporting and activism, or expresses political opinions on social media. Mr. Horse, in particular, identifies himself on Twitter as an anarchist, one of the groups involved in protests on Inauguration Day.

Katy Glenn Bass, the director of Free Expression Policy and Research at Pen America, said that freelance reporters “enjoy the same right to gather information in a public location that all citizens do.” She called the continued prosecution of Mr. Cantu and Mr. Horse “worrying.”

“The U.S. attorney’s office should explain their grounds for the charges against Cantu and Horse or drop them immediately,” Ms. Bass said.