Oman will send a team of investigators to the Tanzanian island of Zanzibar after the collapse of a building known as the House of Wonders from what witnesses said was structural weakness.<br/> Sultan Qaboos bin Said, the ruler of Oman until his death this year, left 5.9 million rials ($15m) in his will for the renovation of the House of Wonders, known in Arabic as Bait Al Ajaib. Built in 1883, it was a seat of the sultans of Zanzibar before the island was united with Tanganyika to form the republic of Tanzania in 1964. “We are very concerned about the news but are still committed to the renovation of the House of Wonders," a statement from Oman’s Ministry of Heritage and Tourism said on Saturday. "We are planning to send a team to investigate the cause of the collapse before we decide on the next course of action.” Witnesses in Zanzibar said a tower on top of the three-floor building collapsed first and crushed the lower floors on Friday afternoon. "The noise was tremendous. I was walking about a 100 metres away on the seafront when it happened. I heard the sound, turned to look and was terrified to see the dust rising to the sky and the whole building front lay in rubble in just one minute," said Khamis Saad, 29, a fruit and vegetable seller.<br/> Zanzibari historians said the House of Wonders was so named because its size and architectural style were breakthough concepts.<br/> "It was the largest building in East Africa at that time and the first one to have a lift. It was the first to have electricity in Zanzibar. It has been a tourist puller and provided a spectacular view for ships calling at the port," said Salim Khalid, 64, a Zanzibari historian. Sultan Qaboos pledged in 2018 to support the House of Wonders' renovation. He died in January after a 50-year rule and was succeeded by his cousin, Sultan Haitham bin Tarek. Oman has historical links with Zanzibar as the island was a colony during the 18th and 19th centuries.