Police say the blast shook the island in the early hours of Sunday morning.
“An explosion occurred at around 1:45 local time (2145 GMT) in a building housing restaurants, bars and shops in Grand Bay,” police spokesman Max Louison said.
A government minister said the explosion may have been caused by gas cylinders.
The blast ripped through the two-storey building causing part of the top floor to collapse.
“We believe that it could be due to the explosion of gas cylinders. We hope it is something like that,” Anil Bachoo, minister of public infrastructure and transport, told Reuters while inspecting the scene.
“We don’t think it’s a terrorist attack as we don’t have terrorists in Mauritius,” he said. He expected an investigation by forensic experts to be finished within 48 hours.
Scores of soldiers helped civilians and police officers remove debris from the site while helicopters buzzed overhead after the blast, which killed a local man and woman in their mid-twenties.
Police said the building had been evacuated. Four of the injured, all believed to be locals, were taken to hospital.
Prime Minister Paul Berenger visited the site, as did officials from the US embassy.
US travel advisory
Tourism is one of the main economic pillars on the tiny island of 1.2 million people, strategically situated between Africa and Asia.
The country has no history of attacks on tourist sites and markets itself as safe for visitors, but the United States issued a travel advisory in March warning of a possible terrorist threat on the island and in the east African region.
More than 700,000 tourists visited the island’s white sand beaches last year, which lie some 4000 km (2500 miles) east of South Africa, bringing in almost $750m in revenue.
Mauritius is also a major regional banking centre and the world’s seventh largest sugar exporter.
It plans to turn itself into a “cyber island” information technology hub linking Asian software expertise with Africa.