A watchdog is investigating whether West Yorkshire Police officers did all they could to prevent a Bradford boy being starved to death by his alcoholic mother.

The Independent Police Complaints Commission has announced it has started a detailed probe into how the force handled concerns raised about the neglect of four-year-old Hamzah Khan and five of his siblings.

Hamzah’s mummified body was found in a cot at his home in Heaton, Bradford, in September 2011, almost two years after he died from starvation in December 2009. Last October his mother, Amanda Hutton, was found guilty of his manslaughter by gross neglect by a Bradford Crown Court jury and jailed for 15 years. Among the issues the IPCC will investigate is why West Yorkshire Police did not refer details of the case to it after Hamzah’s death was discovered in 2011. Instead, it was the IPCC which got in touch with the force after reading media reports of people contacting the police over concerns for the boy and his siblings.

The investigation will look at any contact the police had with the family between Hamzah’s birth and the discovery of his body.

A key part of the probe will be a police visit to Hutton’s house in April 2009, when an officer concluded that Hamzah “appeared to be well.”

Fewer than eight months later he had died of starvation and was subsequently found to be so malnourished throughout his life that he was found in a baby-grow designed to fit a baby aged six to nine months.

A Serious Case Review was carried out by Bradford Safeguarding Children Board following the court case and concluded that Hamzah’s death could not have been predicted, and the only person to blame was Hutton. It said there was no evidence of abuse, and nobody could have taken action to prevent the little boy’s death – despite at least 14 agencies and organisations being in contact with the family. No Council or police staff have faced any disciplinary action in connection with Hamzah’s death. Edward Timpson, Parliamentary Under Secretary of State for Children and Families, has questioned why no follow-up investigation was carried out in April 2009 after Hutton failed to collect some of her children from school.

In response, Bradford Safeguarding Children Board chairman, Professor Nick Frost, said the teacher who returned the children home contacted the police, who immediately carried out a home visit. He added: “Following the visit police reported back to the social work team that the mother and an adult son were spoken to and all six children were seen. The police say the children appeared to be well.”