JOHANNESBURG (Reuters) - At least 36 illegal miners have been killed in an underground fire at a disused gold mine in South Africa and it is too dangerous to search for more bodies, Harmony Gold Mining Co said on Monday. Harmony, the worlds No 5 gold producer, said the illegal miners died at the weekend at its Eland shaft, in the central Free State province, where a similar fire at its marginal St. Helena mine killed 23 illegal miners in 2007. Illegal mining often goes unnoticed because miners can sneak past security at one mine and exit from one owned by a different company kilometres away. Gold prices near record highs have made the risk even more worthwhile. Harmony said illegal miners had brought the bodies of 36 others to the surface at the weekend, but that it was too dangerous to send its own employees on underground searches. It said another 294 illegal miners had been arrested in the province in the past two weeks and would be prosecuted. That followed the arrest of 114 in March including 19 Harmony employees. Harmony, the third biggest gold producer in Africa, was built on a strategy of buying old, unwanted gold shafts and mines, making it particularly exposed to plundering by illegal miners. It is difficult to deal with illegal miners. We dont have the capacity to inspect disused mines and in any case illegal miners are always armed, Thabo Gazi, who heads the mine safety council at the Department of Mining, said. South Africas Chamber of Mines said illegal mining was a problem that individual companies were dealing with, but it had no figures on the value of gold stolen. South Africa is the worlds third biggest gold producer.