Federal agents fired pepper balls and deployed pepper spray to drive back a crowd after two protesters allegedly spit at and hit an officer.

The confrontation is the first skirmish between protesters and federal police since officers cleared the entrance to the U.S. Immigration and Customs Enforcement building on June 28.

The increased tension began Monday morning after a protester repeatedly tore down police tape and stepped across the border of federal property, says Federal Protective Services spokesman Robert Sperling. Federal officers arrested that person.

But another protester resumed tearing down the police tape later in the afternoon, Sperling says. When officers moved to detain the man, he fled to the protest camp. Officers followed.

Protesters and federal police clashed when federal agents attempted to enter the protest camp, which has surrounded the federal building since June 17. Sperling says protesters surrounded the officers and some people spat or hit the agents.

Two people were arrested for assaulting an officer, says Robert Sperling. One of the people arrested was the individual who allegedly fled after tearing down the police tape.

Protesters at the Occupy ICE camp sounded the alarm on social media that officers had fired pepper balls around 1:15 p.m. On Twitter, organizers said that "DHS recently randomly fired pepper balls and arrested peaceful occupiers."

Protesters have a different version of events. They say DHS officers attempted to enter the camp, but a security team called "ICE Breakers" blocked the entrance by closing a gate.

"They proceeded to attempt breaking down the gate and force their way in, but could not," camp organizers said in a statement. After being blocked from entering the camp, organizers say the federal agents "started to fall back to conduct a series of violent arrests," throwing multiple people to the ground and pepper spraying at least four protesters.