The remaining Abuja-Kaduna train hostages are still in detention due to the failure of their captors to honour a deal with the authorities.
Train AK9 operated by the Nigerian Railway Corporation (NRC) was attacked the night of Monday, March 28 between Katari and Rijana in Kaduna.
Terrorists killed more than 10 people and kidnapped 63; about half have been freed with the fate of others hanging.
The insurgents now appear to have backed out of the promise to release the passengers.
Their leadership had entered into a prisoner swap deal that saw the release of 30 terrorists from the custody of security agencies.
An intelligence operative told PRNigeria that the government has taken every possible step, except ransom payment, to get the citizens out.
The source explained that the negotiations remain the best options as a military operation would cause collateral damages.
“Apart from reneging on the agreement, they are releasing the victims in batches, in the most dubious manner.
“They are now exploiting the situation, extorting victims’ families, while other elements are exploiting the same for political gains.
“We are not authorised to strike because of the fear of damages that could trigger massive outcry by rights activists and the media”, the official added.
Military sources said that Bosede Tuwase was among the seven captives released on July 9.
She is the wife of Air Vice Marshal (AVM), Olurotimi Anthony Tuwase, Commandant of Armed Forces Command and Staff College (AFCSC).