Taipei, TAIWAN (AP) — China executed four people found guilty of causing the deaths of six Chinese citizens and running scam and gambling operations out of Myanmar worth more than $4 billion, authorities said on Monday.

The Shenzhen Intermediate People’s Court in south China announced the executions in a statement Monday morning, though it was not clear when they had been carried out.

The executions of 11 other people accused of running scam centers in Myanmar were announced last week.

The Shenzhen court had sentenced five people, including members of the notorious Bai family, accused of running a network of scam centers and casinos, to death in November.

One of the defendants, group leader Bai Suocheng, died of illness after his conviction, the court said.

The group had established industrial parks in Myanmar’s Kokang region bordering China, from where they were accused of running gambling and telecom scam operations involving kidnappings, extortion, forced prostitution and drug manufacturing and trafficking.

They defrauded victims of more than 29 billion yuan ($4.2 billion) and caused the death of six Chinese citizens and injuries to others, the court said.

Their crimes “were exceptionally heinous, with particularly serious circumstances and consequences, posing a tremendous threat to society,” the court’s statement read.

The defendants had initially appealed their verdict, but the Guangdong Provincial High People’s Court dismissed their appeals, it added.

The executions are part of a broader crackdown by Beijing on scam operations in Southeast Asia, where scam parks have become an industrial scale business, especially in Myanmar, Cambodia and Laos. A mix of trafficked and willing labor there have carried out digital scams on victims around the world, including thousands of Chinese citizens.

Authorities in the region face growing international pressure from China, the United States and other nations to address the proliferation of crime.