The driver, cleaner and owner of the truck have been detained, police said.

The Uttar Pradesh government is ready for a CBI probe into the accident of the woman from Unnao, who had accused a BJP legislator of rape, if a request is made, the state police chief said on Monday.

A car in which the Unnao rape survivor, her family and lawyer were travelling was hit by an over-speeding truck in Rae Bareli on Sunday, killing two members while leaving her and the advocate critically injured, police had said.

"The truck was over-speeding and it was raining also. Prima facie, appears to be an accident, but a detailed unbiased probe is on in the matter," Director General of Police OP Singh told reporters.

"The state government is ready for recommending a CBI probe into the Sunday''s mishap in Rae Bareli if the victim's mother or any relative makes any request in this regard," Mr Singh said.

The woman, who had accused Bharatiya Janata Party MLA Kuldeep Sengar of rape, was provided adequate security, the DGP said.

The officer said there was no security lapse in the case. He added that seven security personnel were posted at her home and three were there to accompany her on Sunday. "As there was no space in the car, the survivor did not take the security men with her," he said.

An FIR has been registered in Rae Bareli on the complaint of Mahesh Singh, the woman's uncle who is lodged in a district jail, said Rajeev Krishna, the additional director general, Lucknow zone.

"We have got a complaint in this regard by Mahesh Singh through the jailer and registration of an FIR is in process in Rae Bareli," Mr Krishna said. "He has also given an application requesting a CBI probe into the matter. As soon as we get the letter, as the DGP has already said, a CBI probe may be recommended."

The truck was returning to Fatehpur after delivering red sand in Rae Bareli. The driver, cleaner and owner of the truck have been detained, Mr Krishna said.

On reports that the number plate on the truck was blackened, the ADG said, "As per the owners claim, he did so to hide the number plate as the truck was financed and he did not give due installments".

"We are verifying claims of the driver, owner and eyewitnesses. Tyre marks and sequence of incident are being also considered during probe," he said.

Mr Krishna said the woman and her aunt, Pushpa Singh, who died in the incident, were CBI witnesses and the other two were not.

"It was an accident... If there was any conspiracy behind it, it is a matter of probe. All the allegations are being considered and will be part of the probe," the ADG added.

Meanwhile, Lucknow District Magistrate Kaushalraj Sharma said the state government had decided to bear all the expenses of the treatment of the two injured, who are admitted in the KGMU trauma centre.

After the news of accident spread, Samajwadi Party chief Akhilesh Yadav alleged that it could be a conspiracy to kill her and demanded a CBI probe into the incident.

"This incident has links with a BJP MLA and there is a BJP government in the state. There is 'jungle raaj' in the state. The criminals are roaming fearlessly. Only a CBI probe will solve this mystery," Mr Yadav said.