Police officers are under investigation after a suspected drug dealer died minutes after being gripped by the throat as he was being searched. The Times has learnt that only weeks earlier the same man twice told hospital staff that he had been assaulted by police.

Habib Ullah, 39, of High Wycombe, Buckinghamshire, died from a heart attack as police tried to remove a package containing crack from his mouth. It was removed later from his windpipe in Wycombe Hospital.

According to a pathologist’s report seen by The Times, one of the officers was reported to have said that “he hoped he had not grabbed the deceased’s throat too hard to get the drugs out”.

Mr Ullah’s death on July 3 last year is the subject of an investigation by the Independent Police Complaints Commission (IPCC). The commission has confirmed that it is also looking into claims that Mr Ullah had required hospital treatment after being beaten by police eight weeks before his death.

Mr Ullah told staff who treated him for bruising and an aching back at Wycombe Hospital Accident and Emergency that he had been “hit with a baton and sprayed with gas”, according to medical records seen by The Times. Three days later he returned to the hospital complaining of “body aches” and being unsteady on his feet.

The allegation has angered his family, who believe that Thames Valley Police were responsible for his death and want the officers involved to be questioned on suspicion of possible assault or even manslaughter. They have accused officers of using restraint tactics that were not approved. Once he collapsed, they say, the police failed to make proper attempts to resuscitate him and call an ambulance as quickly as they could.

Eight months after Mr Ullah’s death, Marcus Cottoy, 31, who had also swallowed drugs, was arrested in High Wycombe on suspicion of criminal damage and was taken to a police station, then sectioned to a mental institution, where he died. A post-mortem examination found three packages of white powder in his intestine. One had burst. There was no evidence of assault. Samples of the powder are being analysed.

The two men’s deaths came amid a high-profile clampdown by Thames Valley Police aimed at combating the area’s drug problem. Mr Ullah had been in a car with two companions when he was pulled over in High Wycombe last summer. Correctly suspecting that he had a packet containing drugs in his mouth, two constables and a sergeant attempted to force Mr Ullah to spit it out. The officers forced him to the ground face down with one gripping him by the throat but were unable to recover the package.

Soon afterwards he went limp and had a heart attack. Emma Forbes, his companion, who witnessed the arrest, screamed, “You’ve strangled and killed him!”, according to her interview with the IPCC.

An ambulance took Mr Ullah to Wycombe Hospital where he was declared dead later. A package removed from his windpipe contained crack. A post-mortem examination discovered that he had another bag of the drug hidden in his rectum. It also found that his body was covered in bruises consistent with him being kneed in the back and thigh, poked in the eye, punched and slapped. In his post-mortem examination report, the pathologist, Dr Nicholas Hunt, rules out strangulation as a cause of death. Instead, he blames the heart attack on the stress of the restraint and struggle, along with cocaine toxicity, a blocked windpipe and previous damage to Mr Ullah’s heart consistent with cocaine abuse. “It is,” says Dr Hunt, “clear that this is not an example of a death attributable solely to restraint.”

Mr Ullah’s widow Mussarat is being represented by the solicitor Jules Carey, of Tuckers, who also represents the family of Ian Tomlinson, who died after being hit by police at the G20 protests in London.

The IPCC is awaiting the opinions of experts in the proper use of restraint before deciding whether this should be treated as a criminal rather than a disciplinary matter. Thames Valley Police said its training in safe methods of restraint complied with national training rules and guidelines. However, Mr Ullah’s case and the death soon after leaving custody of Marcus Cottoy have raised questions about the treatment of possible drug users or dealers in police hands.

Helen Shaw, co-director of the pressure group Inquest, which provides advice to the families of people who have died in police custody, said: “Pushing people’s faces to the ground, and neckholds have contributed to previous deaths. Sometimes the question is raised . . . what’s in the police officer’s mind? Are they being objective?”

Operation Falcon, started in 2006, was heralded as Thames Valley Police’s intelligence-led approach to break drug networks. Shona Morrison, the force’s drugs co-ordinator, said: “We are proud of our achievements.”

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