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 the Chinese territory.

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

The woman went to the waterfall inside a park in Pok Fu Lam on Hong Kong Island on Sunday night with the suspect, but he rushed off alone in a taxi after staying there for about half an hour, police said.

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

An initial autopsy showed the woman drowned after being hit in the head with an unspecified hard object. Sin said the woman had injuries to her head and limbs.

The suspect and his wife, a Hong Konger, had gone to mainland China before officers arrested them when they returned to the city on Tuesday, Sin said. The man was detained on suspicion of murder and his wife was held on suspicion of assisting offenders.

The man holds a Hong Kong identity card, but police did not specify which country he or the victim was from.

“We found so many unreasonable things related to the arrested man. He didn't report to the police and immediately left Hong Kong after the incident. Some evidence related to him had disappeared too,” Sin said.

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

"This case involves a person’s life, and we take that very seriously. We will carefully unravel every detail to uncover the truth and to bring justice to the deceased,” Sin said.