Four people have been killed, in South Florida, after two armed jewellery thieves hijacked a UPS truck along with its driver and led police on a high-speed chase that ended in a shootout.

Police fired 200 bullets at the truck during the shootout with both suspects, the UPS driver and a bystander, who was in an idle car as the wild chase came to an end was also in the firing line.

The pair of robbers were after diamonds at the Regent Jeweller's store on the Miracle Mile of Coral Gables.

After entering the store, employees set off a silent alarm which alerted police who were on the scene within a minute and a half.

Authorities investigate the scene of a shooting in Florida. Credit: AP

The truck then led police on a long chase, mounting curbs and performing U-turns around other vehicles and police.

There appeared to be dozens of police officers and vehicles in pursuit of the UPS truck as it sped along through dual carriageways.

By the time the chase ended, more than 40 emergency vehicles were stopped behind the truck, lights flashing and sirens blazing.

When asked whether the UPS driver or the bystander was hit by police fire, the FBI Special Agent in Charge George Piro said that is part of the investigation.

A row of vehicles and a UPS truck are seen behind police tape after a shooting on Thursday. Credit: AP

Piro added: "We have just began to process the crime scene, as you can imagine, this is going to be a very complicated crime scene."

UPS spokesman David Graves said the company would cooperate with authorities.

In a statement, Graves said: "We are deeply saddened to learn a UPS service provider was a victim of this senseless act of violence.

"We extend our condolences to the family and friends of our employee and the other innocent victims involved in this incident."