A group of 25 Chinese workers kidnapped in the north of Egypt's Sinai peninsula on Tuesday have been freed. An assistant to the Chinese ambassador in Cairo said they were all well and had not sustained any injuries. Egyptian officials had been negotiating their release after they were taken by Bedouin tribesmen demanding their relatives, in prison for a 2004 bomb attack, be freed. The attack came days after 29 Chinese workers were kidnapped in Sudan. 'Text messages' An Egyptian security official said the group - said to be cement workers - were returned to their hotel in the provincial capital, el-Arish, early on Wednesday, AP reports. The official, who did not want to be named, said the kidnappers had been promised that their relatives would be re-tried. A Chinese embassy official in Cairo, Ma Jianchun, said he had met the workers and they were "were in good condition", Xinhua said. The workers were seized on their way to a military-owned cement factory in the Lehfen area, south of al-Arish, on Tuesday. The armed kidnappers had called for the release of five relatives jailed after the 2004 bomb attack at the Red Sea resort of Taba that killed 31 people. They claim that Egypt's ruling military council - which took power after the fall of President Hosni Mubarak last year after mass protests - had repeatedly promised to free the Bedouins. One of the workers who had been held for 15 hours, a 25-year-old man with the surname Pan, told Xinhua that the group had communicated with Chinese diplomats via mobile phone text messages. Dangers for workers Correspondents say tribesmen have been involved in a series of confrontations with security forces in recent months. A gas pipeline from Egypt to Israel has also repeatedly been sabotaged, though the big tourist resorts on Sinai's south coast, including Sharm el-Sheikh, have remained largely secure. This latest case highlights the dangers facing China's workers as Beijing pushes to invest in volatile regions, says the BBC's Martin Patience in Beijing. On Tuesday, China sent a team of officials to Sudan to assist in the rescue of 29 workers kidnapped over the weekend. The Chinese nationals had been working on a road project when they were captured by a rebel group in the country's volatile border state of South Kordofan. They have yet to be released. An estimated 60 million Chinese went abroad in 2010 and 75 million were projected to do so in 2011, says AP.