Police are monitoring Alexandra following attacks on temporary Pikitup workers as they tried to clean up rubbish in the township on Sunday night.
Officers had been deployed to strategic locations, police spokesperson Major Mack Mngomezulu said on Monday.
"We are monitoring the situation closely, and after we made some arrests last night the people seemed to calm down. We believe that some of the people who attacked the temporary staff are permanently employed by Pikitup," he said.
Several refuse trucks were attacked and one worker was stabbed while collecting rubbish. One truck suffered damage estimated at R15 000.
The City of Johannesburg said on its Twitter page that nine of its trucks were attacked while collecting refuse in the township, and two people were arrested.
Pikitup spokespeople could not immediately be reached for comment.
About 3000 Pikitup workers affiliated to the SA Municipal Workers Union had been striking illegally for two weeks. They wanted inconsistencies in salary grades addressed and the company's managing director Amanda Nair to resign.