Local government officials are investigating how World Cup tickets they donated to local farm workers ended up being sold illegally outside a stadium.

A spokesman for Ace Magashule, the premier of South Africa's Free State province, said a number of tickets for the match between Japan and Cameroon in the central city of Bloemfontein had been given to poor farm workers from the region.

William Bulwana said it was unclear how the tickets came to be sold by touts outside Free State Stadium at Monday's game. South Africa's Star newspaper said some of its reporters bought tickets outside the stadium.

Bulwana said the local government would make sure "the premier's generosity is not exploited" in the future.

A Johannesburg radio station reported earlier this week that touts were operating freely at the World Cup, offering a $140 ($A163.17) ticket for the final for around $1,600 (($A1,864).

Free State Stadium's next game is Thursday's Group B encounter between Nigeria and Greece.

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