JERSEY CITY - Authorities in Jersey City say 12 firefighters were hospitalized with respiratory problems after they responded to an explosion caused by a bug bomb.

None of the injuries are believed to be serious, according to fire officials. They say the firefighters went to an apartment yesterday morning after receiving calls about an explosion. But no one was home at the time, so they forced their way inside and were soon overcome by fumes.

Authorities say the cause of the explosion remains under investigation.

AP wire services contributed to this report.