U.S., Sept. 24 -- An American tourist, Steven Weber, died while diving underwater at Manta Resort in Zanzibar's twin island of Pemba .

The US State Department has confirmed the death of the Louisiana man, while Tanzanian security authorities said they were investigating the incident.

Weber and his girlfriend, Kenesha Antoine, who had traveled from Louisiana to Pemba Island on Thursday of last week, were staying at the luxury Manta Resort, which is famous for its floating accommodations that include underwater rooms.

"We offer our sincerest condolences to the family on their loss. We stand ready to provide all appropriate consular assistance," the State Department said.

The Manta Resort confirmed in a statement that a guest had died. The...