Police in the Indian city of Mumbai (Bombay) have launched an investigation into the death of a man who was called in for questioning about deadly blasts in the city last week.
Fayaz Usmani died in hospital early on Sunday, hours after he complained of feeling unwell during his questioning.
His family suspects foul play, but police deny allegations of torture, saying he died of a heart attack.
Wednesday's three explosions killed 19 people and injured dozens.
The attacks were the deadliest in India since 2008, when gunmen killed 165 people in a three-day raid in Mumbai.
No group has said it planted the bombs but suspicion among some officials and analysts has fallen on the Indian Mujahideen, a group which has claimed to have carried out similar attacks in the past.
On Saturday afternoon, Mr Usmani was picked up by police for questioning about the blasts.
The police said that within 20 minutes he was complaining of stomach ache and vomited.
Mr Usmani was taken to a local hospital, where examinations revealed that he had suffered from brain haemorrhage. He died early on Sunday.
"Mr Usmani was suffering from hypertension. The allegations of torture by police are absolutely untrue," Nisar Tamboli, a police spokesman, told the Associated Press news agency.
The chief of the hospital where Mr Usmani was admitted said that Mr Usmani had suffered from a heart attack and "no marks of injury were found on his body".
Mr Usmani was the elder brother of a suspect of blasts in the western city of Ahmedabad in 2008, who is now in prison.
His relatives said Mr Usmani did not suffer from any health problems.
His son, Azeem Usmani, told The Hindu newspaper: "He looked fine when he left home. It has happened because of the police."
Separately, investigators are reported to have prepared a sketch of a suspect they want to question over last week's blasts.
Investigators who are going through the security camera footage and forensic evidence from the three sites are hoping to get a breakthrough, media reports say.
The three blasts hit hit Zaveri Bazaar, an area with many jewellery shops, Opera House business district in the south of the city and Dadar district in the city centre.