The probe follows complaints over port company Klasco's iron ore's handling. Prosecutors say they launched the investigation after evaluating information on norm-exceeding air pollution in Klaipėda's northern residential areas adjacent to the port.

"The pre-trial investigation will try to identify the origin and composition of pollutants and those potentially responsible for the pollution," local prosecutors said.

Klasco rejects criticism as unfounded, saying that hundreds of industry, transport and handling companies as well as the badly-regulated traffic are affecting environment.