Seven Seattle Sounders fans were assaulted following Sunday's match between the Sounders and D.C. United, according to a report filed with Washington D.C.'s Metropolitan Police Department.

The report, a copy of which was obtained by ESPN, states that the fans were leaving Audi Field, and were about a block east of the stadium when they were confronted by approximately 12 D.C. United supporters who initiated a confrontation by pushing, punching and kicking the victims.

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According to the report, the injuries sustained by the Seattle fans ranged from minor cuts to "swelling and severe pain" to one victim's jaw. A report from Sounder at Heart stated that the victim with the injured jaw was taken to a local hospital.

The Emerald City Supporters, the Sounders' largest supporters group, put out a statement on Twitter indicating that their members were the victims of the assault, adding that they were assisting the Sounders and the league in "identifying the cowards who perpetrated this unprovoked attack."

League protocol dictates that opposing fans are held for upwards of 30 minutes in an effort to ensure their safety. D.C. United put out a statement on Monday stating that the Seattle fans were held for 20 minutes before being escorted out of the stadium.

D.C. United's statement read in part: "Our sympathy goes out to the injured fan involved in the incident that took place outside of Audi Field following last night's match against the Seattle Sounders.

"We are deeply concerned about this incident and are continuing a thorough investigation alongside the Metropolitan Police. ... We are looking through all our camera footage from outside of the stadium and are working with the District and surrounding businesses to find additional footage to find who was responsible."

In a statement of their own, the Sounders said they were aware of the attack and are in the process of gathering "all the necessary facts in the most thorough and efficient manner possible."

"Our appreciation for our fans runs deep. They are an integral part of our club culture, and the relationship between our fans and the team is what makes our club so special," the statement said. "With this in mind, nothing can be more important than fan safety, and we are taking the allegations of physical altercations seriously. We want our fans to understand that we are working expeditiously to get to the bottom of this matter, and once that process is complete, the organization will provide additional information."