The incident at the Inalende junction, Omitowoju area of the Oyo State capital, happened around 6.30 p.m, while the tanker, with Lagos registration number XJ 288 SMK, was trying to manoeuvre its way at the junction.
After the tanker fell, it spilled its cargo on road, and then exploded.
The raging inferno, the eyewitness said, affected many houses and shops on the street.
The fire was still raging by Monday night while unconfirmed reports had it that some people were trapped in some of the houses and shops already razed by the fire.
But, it was not clear whether any lives were lost.