Martin Lee Anderson was beaten on his first day at the camp

The 14-year-old boy collapsed after running laps on his first day at the camp for juvenile offenders in 2007.

The boy was beaten by guards for 30 minutes and made to inhale ammonia in what they said was an attempt to revive him. He died in hospital a day later.

The jury took about 90 minutes to find the guards not guilty.

Defence lawyers argued that the guards properly handled what they thought was a juvenile offender faking illness to avoid exercising.

They argued that Martin Lee Anderson died from complications linked to an undiagnosed sickle cell trait - a usually harmless blood disorder which can hinder the blood cells' ability to carry oxygen during physical stress.

Camps shut down

But a medical examiner said the "forced inhalation" of ammonia caused the teenager's vocal cords to spasm and block his upper airways, and he died of suffocation.

The boy's mother, Gina Jones, left the courtroom after the verdict was read.

"I cannot see my son no more. Everybody see their family members. It's wrong," she said.

Anderson was sent to the boot camp for probation violations, after he was charged with stealing his grandmother's car from a church car park.

His death led Florida lawmakers to order that all such camps be shut down.

Anderson's family sought a trial after accusing state authorities of trying to cover up the case.

Earlier this year the state legislature paid them $5m (£2.5m) to settle civil claims.

The defendants would have faced up to 30 years in jail if convicted of manslaughter.

The jury could have convicted them of lesser charges, including child neglect and culpable negligence.