LONDON — The South African prison authorities said on Tuesday that Oscar Pistorius, a double-amputee track star jailed for murdering his girlfriend, Reeva Steenkamp, had been bruised in an altercation with a fellow inmate over the use of a public telephone in prison.

While Mr. Pistorius, 31, was not seriously injured, the prison authorities said the events were under investigation. News reports said that Mr. Pistorius, who competed in both the Olympic and Paralympic Games in London in 2012, could lose privileges if found to have started the fight.

The episode was said to have taken place at the Atteridgeville Correctional Center, near Pretoria, which has facilities for disabled prisoners. Mr. Pistorius was born without fibulas and his legs were amputated below the knee when he was less than a year old. He has competed using curved prostheses that inspired the nickname Bladerunner.

Singabakho Nxumalo, a spokesman for the Department of Correctional Services, told South African news outlets that the altercation happened last Wednesday in a special care unit where Mr. Pistorius and another prisoner were incarcerated. During a medical checkup later, Mr. Pistorius was found to have been bruised. The other person involved in the fight was not identified by name.