Tue, 27 Jan 2009 16:25 UTC
The object, described by witnesses as an alien spacecraft, crashed on the playing fields at Yeo Moor Junior School shortly before midnight on Wednesday.
It then took off again but, as well as leaving a trail of debris behind, footprints were also found.
Police are not confirming what it is but a crime scene investigator exclusively told the Mercury 'he had never seen anything like it before' and that in his opinion 'it appeared to be alien'.
Mrs Symes, of Baytree Road, said she was walking her dog at about 11pm on Wednesday when she heard 'an amazing noise'.
She said: "Initially I thought it was an aircraft having trouble, then I spotted this strange-looking rocket-type machine falling to the ground.
"It crashed at the school and there was a huge explosion.
My dog was going berserk and I suddenly felt very frightened so I ran home and immediately called the police.
"When I was on the phone I heard engines start again and saw the rocket take off and disappear within seconds.
"I didn't think the police would believe me, and to start with they didn't, but then they cordoned off the school field."
PCSO Linda Richards was the first person on the scene.
She said: "I have to admit when we spoke to Mrs Symes we thought she was having us on but I still had to investigate.
"When I got to the school everything was quiet but just as I was about to leave I spotted smoke from the corner of the field.
"I then saw that some sort of aircraft had landed on the field, but had taken off again.
"I cordoned off the area so that officers could start investigating at first light and called headteacher Roland Lovett."
Mrs Clark, a learning support assistant who lives near the school, also witnessed the crash.
She said she was worried that no-one would believe her, so was relieved when she realised she wasn't the only one who saw it.
She said: "I was up late preparing school work and heard an amazing noise.
"I had no idea what it was but spotted a machine a bit like a rocket, which was falling to Earth.
"When it crashed there was a huge explosion so my husband and I went to investigate.
"We saw it was at the school but couldn't get in as the gates were locked.
"It definitely looked like something extra-terrestrial to me."
Yeo Moor Junior School was open on Thursday, but pupils were not allowed near the crash site.
Sgt Gareth Starr said: "We are investigating the matter but cannot give any more details at this time.
A spokesman for Bristol International Airport said air traffic controllers reported nothing unusual.