Malaysian authorities have said an investigation is underway to determine the cause of the death of Syed Alman Zain Syed Alwi, the son-in-law of Deputy Prime Minister Ahmad Zahid Hamidi.

Syed Alwi died following treatment at a dental clinic in Bangsar on Wednesday night at the age of 44.

"The investigation started yesterday and it is still too early to come to a conclusion," Health Minister S. Subramaniam said, the New Straits Times reported. He cautioned against the public speculating on the matter.

It is reported that Syed Alman fell unconscious while he was undergoing dental surgery at a clinic in Bangsar at around 6 pm. He was immediately shifted to the University Malaya Medical Centre in Petaling Jaya for treatment but he was pronounced dead.

Syed Alman's remains were brought to the Surau An Nur Country Heights and would be buried at the Muslim cemetery in Kajang.

Several VIPs, including Umno secretary-general Tengku Adnan Tengku Mansor and Armed Forces chief General Tan Sri Zulkifeli Mohd Zin, were spotted at the UMMC Emergency Unit and mortuary.

Ahmad Zahid, who was attending a conference in Japan is said to be on his way back to Malaysia.

Syed Alman was married to Ahmad Zahid's eldest daughter, Nurul Hidayah. His 37-year-old wife expressed her grief at the loss of Syed Alman and posted a picture of the two on Instagram on Thursday.

"Al Fatihah. Syed Alman Zain bin Syed Alwi. Great Papa. Responsible husband. I lost someone that I can argue with. Bye Sayang," posted Nurul Hidayah.