Twenty-eight female guards were unfairly dismissed by a security company because the client‚ Metrora.
Mpumalanga police manning border posts say an increasing number of people are illegally crossing into South Africa.
Twenty two people, arrested when they tried to cross the border fence that separates South Africa and Swaziland, appeared in the Piet Retief magistrates' court on Monday.
They were found guilty and each sentenced to a R500 fine or 60 days in prison.
Mahamba police spokesman Constable Eric Sibisi told Sowetan that the illegal immigrants were arrested after crossing the border next to Mahamba, near Piet Retief.
"We received a tip-off and on Sunday we sent a patrol to the area," he said. "Many were arrested when they tried to sneak in from Swaziland.
"Many of these people are in possession of South African identity documents and claim to be South African citizens."
Sibisi said the offenders told the court that they worked and lived in Johannesburg, and that they had visited relatives in Swaziland.
"When asked why they didn't have SA passports, none of them gave us a reasonable answer."