The FBI says it’s unlikely it could have done more when it first investigated the gunman who shot dead 49 people at an Orlando nightclub.

The gunman, Omar Marteen, was interviewed twice in 2013 after concerns were raised by co-workers.

FBI director James Comey said investigators did the best job they could, but has promised an honest review in their efforts.

‘Our work is very challenging,’ he said.

‘We are looking for needles in a nationwide haystack.

‘But we’re also called upon to figure out which pieces of hay might someday become needles.’