Six British tourists arrested in northern China on 10 July are being deported, the Foreign Office has said.
They were among a group of foreigners detained in Ordos in Inner Mongolia.
Three other Britons and two dual British-South African nationals remain in custody and the Foreign Office said it had requested an explanation for their detention.
A Chinese foreign ministry spokesman told the BBC the group was suspected of “committing crimes”.
China Odyssey Tours – a travel agency based in China – confirmed to the BBC that the group was on one of its tours, but the company would not give any other details about the circumstances surrounding the arrests.
The six Britons released so far are expected to land in the UK on Thursday.
South Africa-based charity Gift of the Givers said it had been contacted by relatives of some of the tourists asking for help.
Dr Imtiaz Suliman, head of the foundation, told the BBC his organisation had negotiated the release of South African hostages held in Syria and other parts of the world and was “known for being good at it”.
The charity said the group – which included nine Britons, 10 South Africans and one Indian national – were supposed to be exploring ancient China during a 47-day trip.
But in a statement on its Facebook page it said the tour went “horribly wrong” when the party were arrested at Ordos Airport last Friday.
“No reasons were given for the arrest. Cellphones were confiscated, there was no access to the embassies of origin nor to their families.
“They were detained without charge with no access to any communication nor to legal representation.
“The Chinese, now trying to find reasons for the detention, suggested that some members were linked to a terror group, to a banned organisation, to watching propaganda videos in their hotel room.”
The charity said the group included doctors and businessmen, and none had terror links.
It said representatives from the British, South African and Chinese governments met on Tuesday to secure the release of 11 of the 20 people being held, but no formal charges had been put to any of those detained.
“The Chinese must be told in no uncertain terms to provide the evidence and proof if the South Africans have terror links, charge them and take them to trial, alternatively, they must release them immediately and unconditionally,” the charity added.
“The conditions in the detention centre, apparently, are not good. Family members are extremely worried and want finality on the issue.”
A Foreign Office spokeswoman said: “Consular staff have visited the group to provide assistance and we have requested an explanation from the Chinese authorities about the reasons for detaining these individuals.”
News of the arrests came as Beijing hosts South Africa’s Deputy President Cyril Ramaphosa, who met China’s Premier Li Keqiang and Vice President Li Yuanchao on Tuesday.