Their accounts for the earlier periods are almost certainly based on oral tradition and for events before the second half of the 15th century they are likely to be less reliable. For these earlier periods the two chronicles sometimes provide conflicting information. The earliest mention of Gao is by al-Khwārizmī who wrote in the first half of the 9th century. In the 9th century Gao was already an important regional power. Al-Yaqubi wrote in his "Tarikh" in around 872:  There is the kingdom of the Kawkaw, which is the greatest of the realms of the Sūdān, the most important and most powerful. All the kingdoms obey its king. Al-Kawkaw is the name of the town. Besides this there are a number of kingdoms of which the rulers pay allegiance to him and acknowledge his sovereignty, although they are kings in their own lands. Ibn al-Faqih (writing c. 903) mentions a caravan route from Egypt to ancient Ghana via Kawkaw. but Ibn Hawqal (writing c. 988) states that the old route from Egypt to the Sudan was abandoned in the reign of the Egyptian ruler Ibn Tulun (ruled 868-884) as some of the caravans were attacked by bandits while others were overwhelmed by the wind-blown sand. The more direct route was replaced by one that went to Sijilmasa before heading south across the Sahara. In the 10th century Gao was already Muslim and was described as consisting of two separate towns. Al-Muhallabi, who died in 990, wrote in a lost work quoted in the biographical dictionary compiled by Yaqut:  Their king pretends before his subject to be a Muslim and most of them pretend to be Muslims too. He has a town on the Nile [Niger], on the eastern bank, which is called Sarnāh, where there are markets and trading houses and to which there is continuous traffic from all parts. He has another town to the west of the Nile [Niger] where he and his men and those who have his confidence live. There is a mosque there where he prays but the communal prayer ground is between the two towns. The archaeological evidence suggests that there were two settlements on the eastern bank of the Niger: Gao Ancien situated within the modern town, to the east of the Tomb of Askia, and the archaeological site of Gao-Saney (Sané in French) situated around 4 km to the east.