SINGAPORE, Sept. 4 -- China has detained 52 Singaporeans over alleged involvement in pyramid-scheme activities in Guangxi, in what could be one of the largest cases involving Singapore citizens held overseas.

The detentions were disclosed on Friday by Singapore's Ministry of Foreign Affairs (MFA) and police, which said the 52 were held during a wider Chinese law-enforcement operation targeting suspected pyramid schemes and related offences, The Straits Times reported.

Chinese authorities are continuing their investigations, while Singapore police have contacted their counterparts for more information.

Singapore's embassy in Beijing and consulate-general in Guangzhou have made three visits to all 52 detainees, Second Minister for Foreig...