A hostage-taking that left about 20 dead and 42 wounded at a Florida gay nightclub early Sunday is being investigated as a terrorist act, officials said.

"Any time we have potentially dozens of victims in our communities, that I think we can qualify that as a terrorist activity. Whether that's a domestic terrorist or international one is something we'll get to the bottom of," said Danny Banks, of the Florida Department of Law Enforcement Office.

Asked whether there was any reason to believe there was a connection to Islamic terrorism, FBI special agent Ron Harper said investigators would be looking into "all angles."

"We do have suggestions that that individual may have leanings toward that particular ideology but we can't say definitively," he said.