South African police said Thursday that five people had died after trespassing into a disused mine, with local media reporting the deaths were caused by a gas explosion.

At least 20 people are believed to be still trapped underground at the Gloria coal mine near the town of Middelburg in the eastern province of Mpumalanga after entering the shafts to try to steal cables.

"So far we have five killed," police spokesman Leonard Hlathi told AFP, saying he had no number of those trapped.

State broadcaster SABC said experts had launched a rescue operation to search for more than 20 people trapped underground.

It added that the group went underground to steal copper cables in the mine, which has been closed for several months.

Police said the group went into the mine between Sunday and Wednesday, and that rescue efforts were being hampered by unsafe conditions and a lack of ventilation.

The body of one person who died was taken out on Wednesday and the other four bodies were recovered on Thursday.

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