Archaeological sites containing iron smelting furnaces and slag have also been excavated at sites in the Nsukka region of southeast Nigeria in what is now Igboland: dating to 2000 BC at the site of Lejja (Eze-Uzomaka 2009) and to 750 BC and at the site of Opi (Holl 2009). The site of Gbabiri (in the Central African Republic) has yielded evidence of iron metallurgy, from a reduction furnace and blacksmith workshop; with earliest dates of 896-773 BC and 907-796 BC respectively. Similarly, smelting in bloomery-type furnaces appear in the Nok culture of central Nigeria by about 550 BC and possibly a few centuries earlier.