Police have obtained a seven-day remand order against a 38-year-old suspect arrested in connection with the murder of a family of four in Tanjung Sepat, Sepang.

According to the New Straits Times, Selangor police chief Mazlan Mansor said they had concluded investigations with the arrest of their sole suspect in the case - the boyfriend of the murdered couple's only daughter.

"With this arrest, we consider the case solved," Mazlan reportedly said at the Kuala Selangor district police headquarters today.

Chia Tee Nang, 73, and Lim Mai Shak, 68, as well as their two grandchildren, Ryan Chia Zeng Xi, 9, and Chia Yuan Bin, 3, were found dead in their home in Jalan Tepi Laut on Wednesday, with their house set ablaze.

According to the report, a police raiding party from the state’s serious crimes division stormed a shoplot in Taman Pusat Kepong in Kuala Lumpur at 1am today and arrested the man, who works at a furniture factory.

The police reportedly had earlier obtained information that the man, who has hearing and speech impairments, had sought treatment at a private clinic for his injuries.

"He had acted alone. The incident was triggered following a financial dispute with the family on the same day of the incident," Mazlan was further quoted as saying.

However, he did not go into details on the nature of the dispute.

Mazlan was speaking after witnessing the handover of duties ceremony of Kuala Selangor district police chief superintendent Ruslan Abdullah to his successor, deputy superintendent Mohd Asri Abdul Wahab.

The police had earlier classified the case as a murder-cum-arson, and a video had also surfaced of a boy claiming that he witnessed a man killing his grandparents.