Security sources said on Tuesday the men, officials in the southern Nigerian state of Delta, were picked up on Monday and were believed to have close links to Ijaw ethnic militants whose month-long campaign of sabotage has cut a tenth of Nigeria's oil supply.
Adebayo Babalola, director of the security service in Delta state, said: "The two men are helping us with our inquiries."
Government officials have expressed confidence that the hostage situation will soon be resolved as negotiations progress on a ransom payment with a person whom they believe to be a credible representative of the kidnappers.
However, the Movement for the Emancipation of the Niger Delta, which says it is responsible for the attacks and the kidnapping, has said it is not in talks with anyone.
In a statement on Tuesday, the group said it would keep the hostages until it wins the release of two Ijaw leaders and $1.5bn in pollution compensation from Royal Dutch Shell for delta villages.
"The hostages are going nowhere"
the Movement for the Emancipation of the Niger Delta
"The hostages are going nowhere," the group said in an email on Tuesday. It said that the people negotiating with authorities were interested only in enriching themselves.
The group, which is also demanding more local control over the delta's enormous oil wealth, denounced Olusegun Obasanjo, the president of Nigeria, as a "thief" and said it would attack assets owned by his family and allies in the Niger Delta.
Unions have threatened to withdraw workers from the delta, which produces almost all the nation's 2.4 million barrels of oil a day, if the security situation deteriorates.
Dozens of people have been killed in raids and bombings by the militia, which have pushed oil prices to four-month highs.