Mr Kumar was found dead at his home on Monday
Labour MP Ashok Kumar, who was found dead at his home on Monday, died from natural causes, police have said.
Mr Kumar, who was 53, had represented Middlesbrough South and East Cleveland since 1997, after becoming MP for the ancestor seat of Langbaurgh in 1991.
His office said his death was "a huge shock" and tributes were paid to him from Westminster and beyond.
Prime Minister Gordon Brown said Mr Kumar was "a tenacious campaigner" and "a warm and incredibly generous man".
A Cleveland Police spokeswoman said on Tuesday: "A post-mortem was carried out this morning and revealed that the 53-year-old died from natural causes."
Chief Constable Sean Price added: "Ashok Kumar was a talented MP who was dedicated to serving his constituents and was always greatly supportive of Cleveland Police.
"I was extremely saddened to hear the news of his death and my thoughts are with his family and friends."
Officers were called to the MP's Middlesbrough home on Monday after his staff were unable to reach him by telephone and raised the alarm.
News of his death was announced in the Commons several hours later by Speaker John Bercow.
Born in India, Mr Kumar became MP for Langbaurgh at a 1991 by-election, but narrowly lost the seat in the 1992 general election.
He stood again in 1997, when the constituency was redrawn as Middlesbrough South and East Cleveland, and won with a 10,000-plus majority.
In recent years, Mr Kumar served as a Commons aide to Environment Secretary Hilary Benn, who said he was "deeply shocked and saddened" at his death.