1.   Such bombs are surrounded by canisters of flammable gas that intensify explosions.

2.   The hostages are being held in a cell surrounded by canisters of cooking gas, and the inmates say they will explode them if the police invade.

3.   The hostages at Aparecida de Goiana are being held in a cell surrounded by canisters of cooking gas that the inmates say they will explode if police invade.

4.   The hostages were in a cell surrounded by canisters of cooking gas, which the inmates threatened to explode if police invade.