Burgas is a quiet resort around 250 miles east of the capital Sofia on the Black Sea coast.
It is popular with Israeli tourists as a cheaper alternative to other Mediterranean resorts, especially for recent high school graduates before they are drafted for mandatory military service.
Although no-one has claimed responsibility for the attack, some believe Bulgaria poses a greater risk to Israeli tourists because of the shared border with Turkey.
Bulgaria's President Rosen Plevneliev was quoted as saying that the attack "does not mean that Bulgaria is a risky destination for tourism".
More top news
Lively start to the week
White House budget officials outlined the information during a telephone call with reporters given on condition of anonymity.
A prison officer is to be charged with gross negligence manslaughter and misconduct in public office in relation to the death of an inmate.