An investigation is under way after a video of a man being repeatedly beaten by Los Angeles police officers was posted on the internet site YouTube.
Mr Cardenas can be heard saying he cannot breathe
The video shows two officers punching William Cardenas in the face and pinning him to the ground with a knee to the neck, while he struggles.
The incident in Hollywood occurred in August and was filmed by a local.
A report by the two officers said Mr Cardenas resisted arrest and they feared he would try to grab their guns.
Los Angeles police chief William Bratton described the footage as disturbing but said an investigation had to be carried out to decide whether or not the use of force was appropriate.
"There's no denying that the video is disturbing," Mr Bratton said. "But as to whether the actions of the officers were appropriate in light of what they were experiencing and the totality of the circumstances is what the investigation will determine."
The two officers have been reassigned to administrative work while the investigation is carried out.
Police say they feared Mr Cardenas would grab a gun
In the footage, the struggling Mr Cardenas can be heard complaining that he cannot breathe as one of the officers presses down on his throat with his leg.
According to an arrest report obtained by the Associated Press, the officers said Mr Cardenas had tried to resist arrest and they had been concerned that he would grab one of their guns as they were trying to handcuff him.
"The suspect's hand covered my partner's gun holster so I yelled at my partner to watch his gun. My partner responded by capping his gun and delivering a left elbow to the suspect's face causing the suspect to let go of him," the report said.
Mr Cardenas suffered cuts and bruises on his arms, leg and face, and received stitches on an eyelid.
In 1992 the acquittal of police accused of the video-taped beating Rodney King prompted riots in Los Angeles.