A mother and her three-year-old son are believed to have been dead “for some time” before their bodies were discovered at a west London flat.

Officers found 36-year-old Poorna Kaameshwari Sivaraj and her toddler son Kailash Kuha Raj at a home in Clayponds Lane, Brentford, shortly before 1am on Tuesday.

Her husband 42-year-old Kuha Raj Sithamparanathan, who was Kailash’s father, was found with stab wounds and pronounced dead at the scene.

He is believed to have fatally injured himself when officers forced entry to the property, the Metropolitan Police said.

The mother and son had not been seen or heard from for more than two weeks, police said.

Officers had initially been called late on Sunday by a family member raising concerns about the welfare of Sivaraj.

Police attended the address “several times” in the early hours of Monday but did not get a reply and after speaking with neighbours as the day went on they became increasingly concerned and decided to force entry, the Met said.

A referral has been made to the police watchdog – the Independent Office for Police Conduct – due to the belief Sithamparanathan fatally injured himself when officers made their way into the flat.

Next of kin have been informed of the deaths and post-mortem examinations are scheduled to begin on Thursday.

Detective chief inspector Simon Harding, from the Met’s specialist crime command, said: “It appears that Poorna and Kailash had been dead for some time.

“This is a murder investigation and my team will work diligently to establish the sequence of events that led to their murders and the death of Kuha Raj Sithamparanathan.

“Our initial enquiries have established that Poorna and Kailash had not been seen or heard from for some time, perhaps since around September 21.”

He said the family had often been seen walking their poodle cross-breed in the local area and asked anyone who had seen them in the past month to contact police “so we can begin to build a full picture of their lives”.

He added that “words cannot sufficiently sum up the devastation that this horrific incident will have on the families of those involved”.

Police officers and forensics were at the scene on Tuesday.

Neighbours at Golden Mile House earlier told of their shock after the deaths of the family of three.

Sheri Diba said the family were “very friendly” and she used to regularly see them taking their dog for walks.

She told the PA news agency: “I’ve always seen them in the lift. They were very friendly. They said ‘Hi, how are you?’ I always saw them together going for walks.

“They were very friendly, nice people.”

Diba, a mother of one, said she had not seen the family for a number of months.