The blaze in a coach carrying Hindu pilgrims killed 60 people. In riots that followed over 1000 people, mostly Muslims, were killed while the Bharatiya Janata Party(BJP) state government was accused of looking the other way.
The four-member railway committee appointed to investigate the fire said it was probably caused by someone cooking or smoking inside the coach.
The "fire in S6 coach of Sabarmati Express can at this stage be ascribed as an 'accidental fire'," the committee said in its interim report.
The railway inquiry is separate from an investigation by a larger government commission and an ongoing criminal trial.
"There has been a preponderance of evidence that the fire in coach number S6 originated in the coach itself without any external input," retired Indian supreme court judge UC Banerjee, who headed the committee, said.
The Gujarat police, which conducted the first probe, rejected the commission's findings.
"It was a carefully planned conspiracy as proved by us," Police Inspector-General Rakesh Asthana said in Gujarat's main city Ahmedabad.
Riots sparked by the train deaths
claimed 1000 mainly Muslim lives
Gujarat police had accused 131 people of taking part in the arson and arrested 104 under an anti-terrorism law.
No one has been convicted and the law was later repealed by the Congress-led government which came to power in May.
Railways Minister Laloo Prasad Yadav - a maverick leader staunchly opposed to the BJP - announced the departmental inquiry in July.
A leader of the BJP, Mukhtar Abbas Naqvi, rejected the Banerjee committee's findings as "politically motivated".
"The timing of the release of the report is such that Laloo thinks he can divert people's attention away from misgovernance and his party's poor administrative performance in Bihar," Naqvi said, referring to the minister's home state which is holding elections next month.