China says it has restored international shipping on the Mekong River, which was suspended after a deadly attack on Chinese sailors two months ago.

Chinese police Saturday started joint patrols with counterparts from Laos, Burma and Thailand to maintain security along the major transportation waterway in the region. Ten cargo vessels escorted by five joint patrol boats set sail from the Guanlei Port in China’s southwestern Yunnan province in a launching ceremony Saturday morning.

The official new agency Xinhua says the patrol boats are equipped with heavy machine guns and 10-centimeter-thick protective walls, while the police officers are equipped with automatic rifles and bullet-proof life jackets.

On October 5, 13 Chinese sailors were killed on a section of the river south of China’s border, known as the Golden Triangle, an area notorious as a haven for drug traffickers. The deadly attack by suspected drug traffickers raised concerns in Beijing about the safety of crews and vessels sailing south through an area rife with drug warfare and smuggling.

The Mekong River flows through China’s southwestern province of Yunnan into Southeast Asia, serving as a major trade route through several countries including Burma, Laos, Cambodia, Thailand and Vietnam.

China reacted angrily to the October attack, sending patrol boats down the Mekong to retrieve stranded Chinese sailors and cargo ships and calling on diplomats from Thailand, Laos and Burma to speed up investigations.

Since then, police in Thailand have detained nine soldiers who are suspected of killing the Chinese sailors and are also thought to have links with a Burmese drug kingpin.