The 29 Chinese workers captured in Sudan last month were released on Tuesday.

Few details of the release were made public, but the Chinese nationals are said to be leaving rebel-controlled territory on planes operated by Red Cross, which helped negotiate a truce between insurgents and the Sudanese government.

The China Daily reported that on Jan. 28, 47 workers were taken when rebels from the Southern People's Liberation Army North (SPLA-N) raided a construction site owned by China's Power Construction Corporation.

One worker died during the attack and 17 managed to escape. They were picked up by Sudanese authorities last week and brought to a safe place.

The SPLA-N is an off-shoot of the Sudan People's Liberation Movement and its militarized arm, the Sudan People's Liberation Army (SPLA).

The SPLA started as a politically motivated rebel group during Sudan's lengthy civil war, but became a legitimate political party after the founding of South Sudan in July. However, the SPLA-N, still considered a separated affiliate of the party, is actively fighting against the government of Omar al-Bashir, the President of Sudan.

The rebel group stated that the Chinese workers were taken after a battle with the Sudanese army, adding that they took the workers for their own protection, according to Voice of America.

China's Ministry of Commerce has issued a warning for Chinese companies in Sudan, urging them to institute stronger safety and security measures.

China is Sudan's biggest trade partner and the two countries amassed $8.83 billion in business in 2010. Sudan is one of China's main oil suppliers.

This [kidnapping] is a casual incident and will not recur. We reiterate the deeply-rooted Sudan-China ties which are witnessing development in all fields. We pledge to enhance the security measures to protect and secure all the Chinese companies operating in Sudan, Isam Awad Mutwalli, Director of the Chinese Affairs Department at Sudan's Ministry of Foreign Affairs, told the state-controlled Xinhua news agency.