Abuja, Nigeria — Nigerian officials say security forces have rescued seven people who gunmen abducted from a train Saturday, in the first such attack in southern Edo State. Another 24 passengers are still missing.

Edo State police spokesman Chidi Nwabuzor told VOA Tuesday that the rescued victims include one adult male, two women, and four children.

He said the abductors left them behind as the armed men fled from security forces.

"Due to pressure of the operatives who are in the bush for the rescue operation, they seem to drop some certain persons and that is why the rescue is by bits," Nwabuzor said. "The deputy commissioner of police investigation has moved his office to Igueben to further the investigation while the operatives are still in the forest combing the area."

Nwabuzor said those rescued were quickly reunited with their families.

They were among 31 people abducted Saturday at a train station by gunmen armed with AK-47 assault rifles.

Police say some passengers were injured in the attack, but nobody was killed.

Nigerian police say they suspect herders in the area were responsible for the attack.

State Commissioner for Information Chris Osa Nehikhare on Monday said one arrested suspect was helping security forces with rescue efforts.

A local community leader told Nigeria's Punch Newspaper the abductors demanded about $1.5 million to release the captives.

Police spokesman Nwabuzor could not confirm the alleged ransom demand.

A wave of kidnappings-for-ransom is one of several security challenges facing Nigeria ahead of February elections.

Nigeria has for years suffered clashes between herders and farmers and attacks from Islamist militants and separatists.

Outgoing President Muhammadu Buhari ahead of his election in 2015 vowed to solve Nigeria's security problems.

His government has been widely criticized for failing to stop the violence.