An estate near Alberton, south east of Johannesburg, is being investigated over whether it had the correct permits to bring in and keep giraffes, the Gauteng agriculture department said on Tuesday.

"It should be explained that permits are required to import or convey game. Permits are not required to keep game on extensive areas. Permits are required to keep game in bomas or small camps," the department said in a statement.

"The department became aware that some animals such as the giraffe were being kept without sufficient browse available to them and the estate was requested to translocate the giraffe to an area with suitable browse."

The department said the question of whether the Meyersdal Eco Estate had the correct permits could only be answered after the investigation was completed.

No criminal charges had been laid yet.

On July 31, two giraffes reportedly removed from the estate were being transported down the N1 highway on a truck when one of the giraffes hit its head on a bridge and died.

The company that transported the giraffe later said the bridge the animal hit was too low.

"We drove at a speed of 48km/h and drove safely under 31 bridges. There was no warning that the Garsfontein bridge was unsafe," marketing officer for Ditjabe Wildlife Services Dirk Boshoff was quoted by Beeld as saying.

"I am not here to kill animals. I only transport them."

Boshoff said regulations were followed. However, engineer for the Gauteng Freeway Improvement Project Ken Harrison told Beeld newspaper that there was nothing wrong with the bridge and that it met all the legal clearance determinations.

The National Council of the Societies for Prevention of Cruelty to Animals (NSPCA) is considering laying charges against the driver and said on August 1 that it was still investigating and considering charges in terms of the Animal Protection Act.