WARSAW (BLOOMBERG) - Four people died and more may be missing following an explosion at Pniowek mine in southern Poland operated by Europe's largest coking coal producer JSW SA.

As many as 42 miners were present in the section of the mine where the accident occurred at 12.15am local time (6.15am Singapore time), the company said on Wednesday (April 20).

Twenty-one are being treated in hospitals. The rescue operation has been halted until the area is secured to avoid another explosion.

The government is in contact with local authorities to provide aid, Prime Minister Mateusz Morawiecki said on Twitter.

The explosion at one of its main mines is likely to affect output at JSW, based in the southern Polish city of Jastrzebie Zdroj.

The accident is clearly negative for the company, which has planned to produce 14.5 million tonnes of coal this year, according to MBank SA's equity analyst Antoni Kania.

JSW shares dropped 0.7 per cent at 10.47am on Wednesday, underperforming a 0.6 per cent gain for the Warsaw's main WIG20 index.