SOREL-TRACEY, Que. 芒鈧珺次元官网网址� Five people that were taken to hospital Thursday morning after an explosion at the Rio Tinto iron and titanium plant in Sorel-Tracy, Que., have been released.

Company spokeswoman Claudine Gagnon says the workers were treated for shock at the hospital and discharged.

The cause of the explosion involving carbon monoxide gas used in the production process is under investigation.

The explosion, which happened at about 4:30 a.m. ET, caused heavy damage at a section of the metallurgical complex northeast of Montreal.

One section of the facility resumed production Thursday afternoon with four others set to gradually come on stream in the evening.

In total, about 1,400 people work at the complex. Gagnon said there were 192 people at work at the time of the incident.

Rio Tinto is one of the world's leading metals and mining firms with about 50,000 workers in some 35 countries.

The Quebec operation manufactures raw materials for the titanium dioxide markets and produces high purity metal powders and pig iron.

Last year, the company announced it would spend $16 million to retrofit one of the furnaces at the metallurgical complex.

The Canadian Press