Onitsha - Two policemen have been arrested on suspicion of helping kidnappers who seized the finance minister's 82-year-old mother, the force said on Wednesday.
Kamene Okonjo, mother of Ngozi Okonjo-Iweala, was abducted on Sunday from her home in Nigeria's oil-producing Delta state, where kidnapping is rife.
"It is a very sad development and our major concern now is to rescue Mama unhurt," Delta State Police Commissioner Ikechukwu Aduba told Reuters by phone.
It was still unclear why the elderly woman was taken, he added.
"I'm not aware the kidnappers are demanding ransom and, even if they are, the police cannot get involved as that would be a signal for others to continue (abductions)," Aduba said.
Criminal gangs regularly abduct people for ransom in Nigeria, but it is rare for them to target members of the political elite.
The finance minister, a campaigner against corruption, has received threats in the past, according to her special adviser Paul Nwabuikwu.
A Lebanese construction worker was kidnapped on Tuesday morning in Delta state despite having a military escort, police spokesman Charles Muka said.
A security source told Reuters three Lebanese construction workers were currently being held captive. Muka declined to comment on the report of the other two abductions.