JUBA: A United Nations official says that South Sudan’s rebels are holding 13 UN contractors in Upper Nile state.

The UN is engaging with the rebels to release the men, UN information officer Shantal Persaud told The Associated Press on Sunday.

The UN earlier said 12 local contractors were detained after the rebels released 18 international peacekeepers Thursday. The rebels captured the men last week when they seized a UN barge carrying fuel along the Nile River. Rebels control the river’s west bank. The UN has bases on the government-controlled east side of the river.

The rebels said they took the vessel because they thought it was delivering weapons to government troops and carried army soldiers and members of the domestic spy agency. South Sudanese nationals working for UN agencies have been kidnapped and killed in the past along the Nile.