Investigators believe parts of a private jet which crashed in Florida and killed all nine on board may have broken off in the air.

The Learjet 60 was bound for the Bahamas from Austin, Texas when it nosedived into a multi-lane highway and exploded on impact.

A tech entrepreneur and his young family, as well as the 20-year-old copilot, were among those who died on Sunday.

The US National Transportation Safety Board (NTSB) said weather conditions would be a major focus of the investigation but that it was struggling to access the wreckage due to a huge crater on the road in Palm Beach which was formed by the jet.

The plane crashed on Military Trail, a six-lane road that features businesses and restaurants, at around 12:50 local time.

“The biggest obstacle that we’re going to have is recovering the major wreckage from the impacted crater on the roadway,” lead investigator Tim Monville said at a news conference on Monday.

The NTSB said the crater, near the entrance to a mobile home park, was partially filled with water because of severe storms. Heavy rainfall and thunderstorms had been reported in the area at the time of the crash.

Debris was scattered across sports fields, businesses and homes in the area.

“We do have some evidence that there was some breakup of the aircraft before impact,” the NTSB’s Tom Chapman said.

“We may find parts of the aircraft some distance away from the actual impact site.”

Officials are also trying to find out whether a cockpit voice recorder was on board at the time of the crash and if it can be recovered.

Flight analysis indicates that the jet was plummeting hundreds of feet per second before crashing.

In air traffic control audio recordings, someone in the cockpit can be heard reporting “moderate turbulence” and that the crew was “managing the ice”.

They can then be heard saying the plane was “picking up precipitation” and “we need to climb”. Moments later, the same voice said the plane was descending at a rate of 10,000ft (3,048m) per minute.

An emergency was declared and they can be heard yelling “we are in an overspeed condition descending 20,000ft per minute”, before saying, “we are going to crash into the ground”.

Seven passengers died on board the flight – named in a joint statement as tech entrepreneur Adam Robinson, his wife Helen Sharp, and their two children – Emma, four, and Charlie, two – as well as Rachael Reed, Charmi Fehr and Anita Maria Cetina.

The pilot was named in media reports as Jeffery Gregory, while Nathalia Filgueiras, 20, who earned her pilot’s licence when she was 17, was reported to be the copilot.

One man in a car on the ground sustained a leg injury.