A huge fire broke out at an industrial park near Rotterdam on Wednesday, setting off chemical explosions, releasing toxic smoke and disrupting shipping between the country's second-biggest city and Antwerp.

The fire started at a Chemie-Pack chemical plant in the Moerdijk industrial zone, about 40 kilometres south of Rotterdam on Wednesday afternoon. The cause of the blaze was unknown and police said there were no reports of any casualties.

However, shipping traffic at the Hollands Diep river, close to the Moerdijk area, was halted, a spokesman for the Dutch ministry of security and justice said.

A spokesman for the Rotterdam port, Europe's biggest, said the impact on traffic between Rotterdam and Antwerp was limited. The petrochemical complexes of Antwerp and Rotterdam are linked by pipeline and an inland waterway. Rotterdam supplies raw materials for Antwerp's petrochemical industry.

A spokesman for Royal Dutch Shell said the company's refinery, which was two kilometers away from the burning chemical plant, was unaffected and that the wind was blowing smoke in the opposite direction from the refinery.

The fire later expanded to an adjacent factory of Finnish engineering firm Wartsila, Dutch media reported. The company has a logistics centre in the area, Wartsila says on its website.

Several big explosions took place at the industrial zone, Dutch agency ANP reported.

There was toxic material in the smoke but it was not known how concentrated, a spokesman for emergency services told public broadcaster NOS. People in the area were advised to stay indoors and shut their windows, the spokesman for the ministry of security and justice said.