Two of ailing former president Nelson Mandela's daughters arrived at the Medi-Clinic Heart Hospital in Pretoria on Tuesday.
Makaziwe Mandela's red Range Rover drove past numerous police officers deployed at the hospital's entrance.
Her car was followed by that of Zenani Mandela, the South African ambassador to Argentina. Unlike other cars entering the hospital, their vehicles were not searched.
Police were stationed outside the hospital, in the Pretoria suburb of Arcadia. Security at the facility had been tightened, with police officers manning the two entrances.
Police spokesman Brigadier Phuti Setati earlier said police stationed at the hospital were part of the presidential protection services team, whose task includes protecting former presidents.
He did not specifically confirm that Mandela was in the hospital.
Mandela was admitted to a Pretoria hospital in the early hours of Saturday morning in a "serious but stable" condition, the presidency said.
The number of news crews camping outside the hospital continued to swell on Tuesday.
By 11am, there were 13 outside broadcast vehicles along the street near the hospital's main entrance. Hundreds of media personnel, including logistical and technical staff, milled outside the main entrance.
Some of the media crews had generators and erected tents at the second entrance, adjacent to a busy street leading to the Pretoria CBD.
Local and international journalists were also camped outside Mandela's Houghton, Johannesburg, home. Some members of the public took photos of each other outside the house.
Earlier on Tuesday morning a group of school children from the Rainbow Hill Christian School in Orange Grove arrived at the house and sang "Get well Tata Mandela, get well".
After they finished, one boy stepped out of the group and read from a card, thanking Mandela for what he had done for South Africa, wishing him the best, and saying he was loved.
On Monday, the presidency said Mandela's condition was "unchanged" from Saturday and that he was receiving intensive care.
"President Jacob Zuma reiterates his call for South Africa to pray for Madiba and the family during this time," spokesman Mac Maharaj said.
All vehicles entering the hospital premises were being checked and searched.
Barricades were erected at the spot where journalists had been camping on Monday, forcing the press to move across the street. Police tape was used to cordon off the area.
This was the third time this year the Nobel Peace Prize laureate had been in hospital. At the end of March and in April this year he spent nine days in hospital receiving treatment for recurring lung problems.
Earlier in March, he was admitted to a Pretoria hospital for a scheduled check-up and discharged the following day.