Nairobi, Rajab 7, 1433, May 28, 2012, SPA - An explosion rocked central Nairobi on Monday, with witnesses reporting at least one dead and several injured, according to a report of DPA. Some witnesses told journalists that four grenades were thrown, although there has been no official confirmation on the cause of the explosion, which took place just after 1pm (1000GMT). Police have cordoned off the area and rescue workers are at the scene. A huge column of black smoke rose above high rises surrounding a small network of market stalls on the busy Moi Avenue, the site of the blast. At least 20 people have been admitted to hospital with injuries and one man had been arrested, Citizen TV reported. --SPA 14:33 LOCAL TIME 11:33 GMT www.spa.gov.sa/1002564