The wrong mixture of products being loaded or unloaded at the factory of Simar, a chemical distribution company in the Spanish town of Igualada, created an explosion or chemical reaction, resulting in a large orange chemical cloud that hovered over the area.

Local authorities had to inform about 64,500 residents to remain indoors for about one hour with their windows closed.

Like Us on Facebook

But the order was extended to four hours for pregnant women, children, seniors and people with respiratory problems, reports ABC.

Igualada is situated about 70 kilometers north-west of Barcelona. The order to remain indoors went beyond the town to include four other nearby municipalities.

The image of the orange cloud was captured by residents of the affected area and shared in social media sites.

Karina Kosina tweeted that the photos of the clouds "look like framegrabs out of an apocalyptic movie."

The regional Catalan government, in a statement, explained the cloud could have been the result of a reaction with the mixture of nitric acid, ferric chloride and a third unidentified chemical.

Nitric acid, besides being corrosive, is also toxic.

The industrial accident also injured three people, the two workers who were transporting the chemicals and another employee at the factory.

A study by Catalan researchers, published in the May 2014 edition of Agenciasinc.es, said that past chemical accidents in Spain have led to improvement of safety of transporting chemicals as well as industrial processes.

Among the more deadly ones are the explosion in 1978 of a lorry tanker full of propylene while in the Los Alfaques campsite in Tarragons that killed more than 200 people, a cargo vessel loaded with toxic substances that ran aground in 1988 at the Finisterre coastline that led to the evacuation of 20,000 and a deflagration in 2003 at the Puertollano refinery that killed 9 people and injured many more.

Tagsorange cloud, chemical accident, Spain