16 more indicted in Turkish embassy brawl Two have already been arrested.

 -- Federal prosecutors have filed criminal charges against 16 people for allegedly assaulting protesters outside the Turkish ambassador’s residence when President Recep Tayyip Erdogan visited last month.

The incident was caught on camera and caused a diplomatic crisis, with Turkey and the U.S. summoning each other's ambassadors and members of Congress expressing outrage.

Two of the defendants are American citizens and were arrested yesterday. Sinan Narin, 45, of Virginia plead not guilty in a D.C. court Thursday afternoon, and Eyup Yildirim, 50, of New Jersey, is in custody in his home state and awaiting extradition to D.C.

Two other defendants are Canadians, while the rest are Turkish nationals -- 9 security officers and three police officers, all part of Erdogan’s entourage. The State Department tells ABC News they are considering taking additional action against those individuals overseas, which could mean barring future entry or revoking visas.

The violence erupted on May 16 when Turkish security officials and counter-protesters clashed with demonstrators near the ambassador’s residence, where Erdogan stayed after meetings with President Trump at the White House. The incident left 11 people injured, nine of whom were hospitalized.

At the time, two men were arrested and charged with simple assault. The cases for Ayten Necmi, 49, of New York and Jalal Kheirabaoi, 42, of Virginia remain pending, but both men have plead not guilty.

Altogether, today's indictments bring the total number of individuals charged to 18.

Some Turkish security officials were briefly detained at the time by U.S. law enforcement for their role in the brawl, but they were released on the scene because “customary international law affords heads of state and members of their entourage with inviolability from arrest and detention,” a State Department official told ABC News at the time.

It is unclear if an official request for extradition has been extended to Turkey -- or Canada -- but State Department spokesperson Heather Nauert said Thursday that the U.S. was looking at “additional steps” and warned that if any of the individuals sought U.S. visas in the future, “We know that they have warrants out for their arrests.”

Similarly, the Washington, D.C. police chief said the department would arrest any of the individuals if they returned to the U.S., although he would rather they turn themselves in.

“If you are a law-abiding person and you feel like you did not do anything wrong, then please present yourself here to answer to these charges. We’d like to hear what you have to say,” said Chief Peter Newsham. When asked what about those who aren’t law-abiding, he added, “That remains to be seen.”

Days after the incident, video emerged from the Voice of America news agency that also appeared to show Erdogan watching over as the fight unfolded. D.C. police said Thursday that he will not face charges at this time.

“We don’t have any information right now to suggest that we have probable cause to make an arrest of the President,” said Newsham.

Turkey has protested the indictments against its security personnel, summoning the U.S. ambassador to Turkey to their foreign ministry.

“This decision taken by U.S. authorities is wrong, biased and lacks legal basis,” the Turkish foreign ministry said in a statement, blaming “the brawl” on “the failure” of U.S. officials.

“This incident would not have occurred if the U.S. authorities had taken the usual measures they take in similar high-level visits, and therefore that Turkish citizens cannot be held responsible for the incident that took place,” they added.

Members of Congress from both parties have expressed their continued outrage over the incident, with senators John McCain, R-AZ and Claire McCaskill, D-MO both calling for the expulsion of Turkey's ambassador.

At least one senior Republican welcomed the news of today's indictments. Rep. Ed Royce, R-CA, chair of the House Foreign Affairs Committee, said he was “encouraged by the U.S. Attorney's action,” but called on the State Department to go even further.

“The State Department should double down on efforts to help bring these individuals to justice,” he said in a statement, including rejecting a proposed $1.2 million sale of semi-automatic handguns and ammunition to Turkish security forces. “These types of unprovoked attacks on innocent Americans and their Constitutional rights can never happen again.”

Hours before the bloody incident unfolded, President Trump stood side by side with Erdogan in the Roosevelt Room, praising him and promising a new era of Turkish-American relations.