HELSINKI, March 19 (Xinhua) -- Major leak of ammonia occurred at a fertilizer production plant in Uusikaupunki, western Finland, on Tuesday morning, local media reported.

The accident took place as liquid form ammonia was offloaded from a transport. A "remain-indoors" alert was given in the town, but was called off in less than an hour.

Juha Virto, the manager on duty at the regional rescue service, told national broadcaster Yle that a cloud of gas formed over the area. "But luckily the cloud drifted towards the sea."

Two employees of the plant were impacted by the gas but they had protective clothing.

The Finnish safety and chemicals agency Tukes told local media on Tuesday it considers setting up an investigation.

The plant belongs to the Norwegian company Yara and employs 240 people. It had been inspected by last year. It is under special surveillance due to the high risk operations there. Yara said they had a comparable accident in 2013 at the same location.