A Pakistani guard shot and wounded two Chinese nationals working in a textile mill in the southern port city of Karachi on Tuesday, but authorities said the attack was not related to militant violence.

China has frequently demanded better security for its nationals working in Pakistan. Last month, two Chinese were killed in a suicide car bombing outside the Karachi airport.

Thousands of Chinese are in Pakistan to work for Beijing’s multibillion-dollar Belt and Road Initiative, which is building major infrastructure projects. An unknown number of Chinese are also working at factories in the country.

Suhail Jokhoio, the spokesperson for the provincial home department, said the guard involved in the textile mill attack was arrested and police are still investigating to determine why he opened fire.

He said the wounded Chinese were taken to a hospital.

Pakistan has said it is committed to providing full security to Chinese workers.

“Pakistan remains resolute in bringing to justice the responsible individual,” the Foreign Ministry said, adding it was in close contact with the Chinese embassy in Islamabad. Deputy inspector general of police Azhar Mahesar said they were investigating the incident.