After preliminary investigations,the CB-CID Special Investigation wing led by Sub-inspector Ganesh Balan found that 10 container lorries and tipper-lorries from Dindigul had crossed the check post at Samayapuram near Tiruchirappalli on the morning of the fateful day.
They also inquired and collected all details of the lorries, sources added. Chief Minister Jayalalithaa had ordered a probe, saying people and her partymen suspect there was "some mystery" about it.
The 60-year-old Pitchai, in-charge of Environment, Pollution Control and Minorities Welfare portfolios, died on the spot when his car collided with a lorry at Tiruvelankurichi, about 40 km from Tiruchirappalli.
The lorry had sped away. The car driver had told police that the lorry with Kerala registration had "deliberately" swerved towards the minister's car and hit the spot where Pitchai was sitting, and he suspected that it was not an accident.