Crown prince and fashion designer Khalid Al Qasimi was pronounced dead at age 39 on Tuesday.
Son of Sheikh Dr Sultan bin Muhammad Al Qasimi, the ruler of the Emirate of Sharjah in the United Arab Emirates, died in "unexplained" circumstances UK authorities said and CNN reported.
Post-mortem exams failed to explain the cause of death. According to British tabloids such as the Daily Mail, Al Qasimi died after a drug and sex fueled party in his London penthouse.
Starting on Tuesday, the UAE commemorated the prince with three national days of mourning with the flags at half-mast, Fox news reported.
The funeral was held on Wednesday in Sharjah where thousands came to mourn.
Al Qasimi's death comes 20 years after his older brother died from a drug overdose in the family's home in East Grinstead, the Guardian reported.