Police have launched an investigation into a burglary at a luxury mansion owned by the family of the late billionaire Cheng Yu-tung on Hong Kong Island on Thursday.

At 5:46am, police received a report from a domestic worker at the residence on Repulse Bay Road that she had found a window on the second floor had been pried open and the ground floor of the house had been ransacked, Apple Daily reported.

Police arrived to investigate. An initial check found that some gold, jewelry and gold coins had been stolen, but the value of the missing items was still being estimated.

It was understood that Cheng Kar-shun, the eldest son of Cheng Yu-tung and the current chairman of New World Development Co, and his family members were not in the mansion when the burglary took place, news website HK01.com reported.

It was the second time in two years that the mansion had been burglarized. In a break-in on August 8, 2016, some decorative gold items in a corridor were stolen.

The 61,375-square-foot (5,701-square-meter) mansion named Estrellita  boasts a swimming pool, garden and tennis court protected by a 7-meter-tall wall and a security fence.

Other security measures include seven surveillance cameras, security guards and dog patrols.