HONG KONG (AP) — A foreign man living in Hong Kong has been arrested on suspicion of killing a Southeast Asian woman at a waterfall inside a park in Chinese territory.

The woman, about 25 years old, was a domestic worker in Hong Kong but did not work for the suspect, police chief Sin Kwok-ming told reporters on Tuesday night.

Police said the woman went with the suspect to a waterfall in a park in Pok Fu Lam on Hong Kong Island on Sunday night, but the suspect stayed there for about half an hour and then took a taxi alone and left.

On Monday morning, residents saw the woman’s body floating in the pond below the waterfall, Sin said.

An initial autopsy showed that the woman was strangled after being struck in the head with an unspecified hard object. Sin said the woman suffered injuries to her head and limbs.

Sin said the suspect and his Hong Kong wife had traveled to mainland China before officers arrested them when they returned to the city on Tuesday. While the man was detained on suspicion of murder, his wife was also arrested on suspicion of aiding criminals.

The man has a Hong Kong ID card, but police did not say which country he or the victim was from.

“We found a lot of illogical things about the arrested man. He did not inform the police and left Hong Kong immediately after the incident. Some evidence related to him had also disappeared,” Sin said.

The investigation was continuing. The man and his wife remain in custody and have not been charged as of Wednesday morning, police said.

“This case involves one person’s life and we take it very seriously. “We will carefully unravel every detail to uncover the truth and bring justice to those who died,” Sin said.