GUMI -- A toxic chemical known as trichlorosilane leaked from a factory in Gumi on Tuesday, causing seven people to be taken to hospital, officials said.

The leak occurred around 1:47 a.m. at the plant belonging to KEC, a semiconductor manufacturer, in this city some 260 kilometers southeast of Seoul. The seven people were reportedly not in critical condition.

Trichlorosilane, used in the production of semiconductors, is a colorless liquid that smells of hydrogen chloride and can cause breathing difficulties, headaches and dizziness if inhaled.

If inhaled for a long period of time, the chemical can also cause troubles in the digestive system, and if ingested, can lead to vomiting and low blood pressure.

North Gyeongsang Province officials alerted residents to the leak via text message around 2:43 a.m., in what critics said was a belated response.

Firefighting and municipal officials went to the scene to prevent further leakage and had the situation under control by 3:22 a.m.

An investigation is under way to determine the scope and cause of the leak.

"Without knowing the extent of the leak, a massive evacuation could have led to accidents, so we advised residents to close their windows and remain at home for now," a Gumi city official said.

Police said they plan to question factory officials once the emergency is under control.

Gumi has seen a series of chemical accidents in recent years due to the high concentration of factories in the city.

In 2012, five people were killed and more than 3,000 injured as a result of a hydrofluoric acid leak from a plant. (Yohnap)