Passengers travelling south from Centurion to Midrand were trapped for hours on the train, which had its doors closed and little ventilation, according to Marzanne de Villiers, a regular commuter.

The train, which left Centurion station at 7.21am, had encountered a technical problem, according to Gautrain spokesman Kelobogile Machaka.

''In accordance with the train safety protocols, the train was brought to a safe stop and an alternative train was dispatched to rescue [the passengers],'' she said.

De Villiers said the train was delayed for close to three hours, but Gautrain claimed it was about 90 minutes.

''They probably did the best they could, but it looked as though they did not have a proper contingency plan,'' she said.

The train's doors were opened only after a pregnant woman had a panic attack.

When passengers eventually disembarked to board the "rescue train", they had to jump ''from a height of almost 2m''.

Machaka said the transfer was lengthy for safety reasons.

Follow-on trains along the Park station-Hatfield line continued operating normally but were slightly delayed.

''Initial investigations suggest that the technical fault was [attributable to] a computer monitoring equipment,'' said Machaka.