A novel coronavirus outbreak that began in the Vietnamese city of Danang more than a week ago has spread to at least four city factories with a combined workforce of about 3,700, state media has reported.

Four cases were found at the plants in different industrial parks in the central city which collectively employ 77,000 people, the Lao Dong newspaper said.

Vietnam, praised widely for its decisive measures to combat the coronavirus since it first appeared in late January, is battling new clusters of infection having gone more than three months without detecting any domestic transmission.

Authorities have reported one new case linked to Danang, a tourism hot spot where a case was detected on July 24, Vietnam’s first domestically transmitted case in 100 days.