The incident occurred at house number 40 at about 2pm at Zomi street off Upper Sakponba road in Ikpoba Okha local government area.
Residents who were at home when the explosion occurred said they heard a loud sound that shook their houses.
The explosion shattered windows of houses in the area.
Two persons were seriously injured in the blast but no live was lost.
It was gathered that policemen recently raided the house looking for kidnappers.
Some said the house was used as the kidnappers hideout before police swooped on them and some of them ran away.
A 70-year woman living opposite the building who gave her name as Hannah said she heard a large sound.
A tenant in the building who gave his name as Chinedu Elue when the explosion occurred said he decided to do some cleaning after an electrician came to work in his apartment.
He said he went out to buy ice cream after setting fire on some dirt when he heard explosion.
Chinedu said he recently moved into the apartment and that another family living in the house was not at home.
Men of anti-bomb squad led by DCP Musa UBA detonated other explosives found in the compound.
Residents in the area stood at a distance and watched in fear.
Inside the building, the place where the bomb exploded left hole on the ground.