KUNMING -- Police in Southwest China's Yunnan province have busted a cross-border drug-trafficking gang, with 7 suspects detained, authorities said Tuesday.

About 31 kg of heroin and 7.7 kg of methamphetamine have been confiscated, according to the railway police in Kaiyuan city.

Police received a tip-off in December last year that a Yunnan resident was smuggling drugs from Myanmar to China, and the ensuing investigation netted three suspects in March.

In October, four more suspects were caught in the provinces of Hubei and Hunan.

Investigators found that the suspects smuggled drugs from Myanmar to Chinese localities by car or parcel delivery services.