Umaru Yar'Adua, the Nigerian president, has instructed security forces to ensure her safe release.
The president "has directed the security agencies to make every possible effort to ensure that she is returned to her family unharmed and he remains in touch with all efforts being made to secure the girl's release," according to a statement from his office.
Police say they will not use force to free the girl, seized by unknown gunmen while the car taking her to school idled in traffic. Felix Ogbaudu, the rivers state police commissioner, reported no breakthroughs on Saturday.
Oluchi Hill had previously said her daughter was being fed only bread and water and that the gunmen said they would kill the girl if the parents did not meet their demands, including one that the father take his daughter's place.
Her British father, Mike Hill, has lived in Nigeria for years and works in the energy industry. He also runs a popular nightspot in Port Harcourt.
The region's main armed group, the Movement for the Emancipation of the Niger Delta, said its fighters would help search for the missing child, and echoed the revulsion many Nigerians feel towards the kidnapping of children.
Kidnappings in the region have focused mostly on foreign, male workers of international companies presumed to have the resources for ransom payments.
More than 200 foreigners have been kidnapped since fighters stepped up their activities against the oil industry in late 2005 and more than 100 expatriates have been seized this year alone as criminal gangs took up the practice.
Two children of wealthy Nigerians have been seized in the restive Niger Delta in recent weeks. Both were released within days, without injury.