An explosion at Zimbabwe's biggest grain depot reportedly left at least four workers dead while three others were severely injured this week. According to the state-owned Chronicle newspaper, the massive explosion at the Grain Marketing Board’s Lions Den deport in Mashonaland west province ripped through concrete structures and caused fire.The depot's authorities said they were able to put out the fire after a local farmer provided them with a browser, and a quick response from nearby fire departments. Lands, Agriculture and Rural Resettlement Minister Perrance Shiri described the incident as “unfortunate”, adding that it was “too early for speculations” as investigations were under way.A report by the Zimbabwe Broadcasting Corporation (ZBC), said that the plant was the biggest in the southern African country and was of strategic importance. It was unclear how the explosion would affect the country’s food security. * Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.