KIEV, Aug. 2 - Ukraine's major producer and exporter of iron ore, Poltava HOK, suspended production and evacuated workers Wednesday after release of an unknown gas at the production site, a company official said Thursday.

No workers were hospitalized, although some workers had reported minor sickness, the official said. A total of 174 workers were evacuated, the official said.

“We know what to do in situations like that,” the official said. “We work closely with the staff of the emergency situations ministry.”

Poltava HOK, owned by Ferrexpo AG, produced 8.6 million metric tons of iron ore pellets, up from 7.8 million tons in 2005 and 7.4 million tons in 2004, supplied 50% of overall iron ore imports by Central and Eastern Europe last year.

The company’s principle line of business is mining, processing and selling iron ore in the form of pellets for use in the production of steel. Its operations are vertically integrated as it processes all the iron ore it mines and produces substantially all the iron ore concentrate it processes.

The official said the company could not establish what caused the release of the unknown gas, and asked the emergency ministry personnel to investigate the matter.

The official said Poltava HOK has already been briefly suspending and then resuming production over the past week due to the release of the gas. The latest release of the gas is apparently the biggest over the period, the official said.

The development comes less than two months after Ferrexpo has raised $420 million by selling 12% of its shares through an IPO at the London Stock Exchange.

The IPO, the first by a Ukrainian company on the LSE, valued Ferrexpo at more than $1.67 billion, helping to raise cash the company seeks to spend on development and acquisitions.

Ferrexpo, capitalizing on new mining methods and development of new deposits, plans to boost production to 16 million metric tons of pellets by 2014. The company also plans to produce annually at least 3.5 million tons of additional saleable concentrate, which it doesn't currently produce. (sb/ez)