Bengal Chief Minister Mamata Banerjee on Monday expressed doubt about the cause of a minor girl's death which her family attributed to gang rape, and wondered if the class 9 student of Hanskhali in Nadia district died after a fall following a slap by someone.

Asserting that the victim had an affair with the accused, a Trinamool Congress leader's son who was arrested, Banerjee wondered if she was pregnant.

The chief minister also asked why the girl's family members lodged a police complaint five days after her death and cremating the body.

Opposition parties described Banerjee's statement as "shocking" and alleged that she seeks to shield the accused as he is the son of a leader of her party.

The girl died after she was allegedly gang-raped at a birthday party at the house of the accused on April 5. She was bleeding profusely when she returned home and died later that night, according to her parents who lodged a police complaint on April 10.

"The police are yet to understand the cause of the death. I had asked them. Will you call it rape or was she pregnant? Was it (the fallout of) a love affair? Have you enquired about these? This is an unfortunate incident," Banerjee said while inaugurating the Biswa Banga Mela Prangan here.

She said that her family members and local people knew about the affair between the girl and the accused.

"You (girl's family) also conducted the last rites of the body. I am talking as a layman. From where will they (police) get the evidence whether she was raped or she was pregnant or there was any other reason such as she was slapped by someone after which she fell ill," Banerjee said.

A detailed investigation is being carried out, she said adding that she will ask the state commission for protection of child rights to take up the case.

The girl died on April 5 and the police got the information on April 10, the TMC supremo said and asked about the cause of the delay.

The opposition BJP panned Banerjee for her comment and wondered whether her remarks were aimed at influencing the probe.

"Shocking statement by Bengal CM Mamata Banerjee, who trivialises the brutal rape and murder of a 14-year-old girl in Nadia's Hanskhali. She questions the victim and asks if it was a love affair or a case of unplanned pregnancy gone awry! Because the accused is TMC leader's son, senior BJP leader and the party's co-in charge of West Bengal, Amit Malviya, tweeted.

Echoing him, the Leader of the opposition Suvendu Adhikari said such kind of comments only prove how Banerjee is trying to influence the probe and shield the culprits.

When any such incident occurs in BJP-ruled states, she is the first to protest against it. But when similar incidents take place in West Bengal, she tries to shield the culprits. It is shameful that despite being a woman chief minister, she is making such comments. This is the real picture of the lawless situation of Bengal, he said.

The CPI(M) and the Congress also slammed Banerjee for her comments.

Leader of the Congress party in Lok Sabha and state Congress chief Adhir Ranjan Chowdhury claimed that several such incidents happening in West Bengal go unreported.

"We don't get to know about them. Now we have come to know about this incident. What has happened is horrific. The ruling party is trying to influence the probe, he said.

Senior CPI(M) leader Sujan Chakraborty alleged that the incident proves there is lawlessness in Bengal.

The ruling TMC condemned the incident but said it should not be politicised.

The police are investigating the matter and have also made an arrest. Let the investigation be over. The opposition should not try to politicise the matter, TMC spokesperson and state general secretary Kunal Ghosh said.