Four Britons have been arrested following a drugs raid at an English language school in eastern China.
They were among 16 foreign nationals seven teachers and nine students who were held last week after police raided the school in the city of Xuzhou.
Another three Chinese nationals were also detained in the operation in Jiangsu province, north of Shanghai.
No details of the type of drugs involved, or the ages and identities of those involved, have been disclosed.
A Foreign Office statement said: "We are in contact with the Chinese authorities following the arrest of four British people in Jiangsu province, and are providing consular assistance."
Authorities in Xuzhou posted a statement on Chinese social media site Weibo earlier this week saying police had successfully cracked a drug-related case.
Eighteen people were said to have been placed under administrative detention, which carries a maximum detention period of 15 days.
One person was placed in criminal detention a procedure that usually leads to a formal arrest and an indictment.
The arrests involved people working for Education First, a Swiss-based English-language school.
In a statement, the school said: “The alleged drug offences were limited to seven of our teachers and did not take place during working hours or impact any students. The other individuals involved in this incident are not EF students or employees.
"We take the allegations very seriously and we are fully cooperating with the authorities on this matter. All centres are operating normally.”
The company opened its first branch in China in 1998 and has around 2,000 English teachers based in the country.
Official advice on the UK Government website warns of "extremely severe penalties for drugs offences in China, including the death penalty".
It adds: "The Chinese authorities undertake random drug testing on foreign nationals including on entry to the country. If you test positive, the Chinese authorities can prosecute you regardless of where or when you consumed drugs."
China sentenced two Canadians to death on drug trafficking charges this year, sparking a diplomatic row with Ottawa.
There are extremely severe penalties for drug offences in China, including the death penalty.
