A law enforcement official says federal investigators have discounted a claim of responsibility for the New York City bombing on the social blogging service Tumblr.

The official says investigators looked into it and don't consider it relevant to the case.

The official was not authorized to discuss an ongoing investigation and spoke to The Associated Press on condition of anonymity

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Manifesto: This 'manifesto' of the 'NY Bomber' appeared on blog site Tumblr Sunday and now it is has been discounted from investigations

Device: Two devices were found in Chelsea. This, the second unexploded device, is made from a pressure cooker. The blogger says these were just tests and that more bombs would follow

Injuries: The detonation, which went off near this metal box, injured 29 people

Earlier in the day, another official said that the FBI was aware of the posting and evaluating its authenticity.

The Saturday night blast in Manhattan injured 29 people.

Authorities have not yet determined who is behind the blast or a motive.

New York Governor Andrew Cuomo said it didn't appear to be linked to international terrorism.

Earlier an individual claiming to the be 'the NY bomber' announced on a blog that they had bombed Manhattan Saturday in response to 'LGBTQ+ oppression' and that more bombs would follow.

'I don't know exactly how I feel about taking human lives,' begins a post titled 'Taking a human life.' 'However, what I do know is that if I don't do what needs to be done nobody will pay attention.'

The now deleted Tumblr account claimed that LGBTQ people are more likely to commit suicide, but that 'nobody cares'.

It asks 'what if people from the LGBTQ+ community started lashing out in response to the violence and oppression we face with violence and possibly oppression?

'I'm sure that would give people a reason to not stand by while so many people are being oppressed.

'I suppose I'm just going to have to move forward knowing that what I am doing had a purpose and will in fact make a difference.

'I'll keep you all posted,' it concludes.

Anti-Trump: The writer in the blog described Trump as 'misogynist, xenophobic, racist, Islamophobic'

The Tumblr account is titled 'I'm the NY bomber' and subheaded 'This is will be (sic) my manifesto,' and has gay pride flags as its images.

On one, the words 'Whats (sic) wrong with homosexuality' are written.

An earlier post, titled 'Manufacturing Test Explosives,' said the Chelsea bombs were 'just some tests,' adding 'I will not make the same mistake next time'.

'I did it because I cannot stand society,' the writer claimed. 'I cannot live in a world where homosexuals like myself as well as the rest of the LGBTQ+ community are looked down upon by society.'

The writer said they would 'not stand by while under classed and underprivileged people are oppressed,' or while 'racism (is displayed by) white police officers all over the country.

'I am not going to live in a country where it is OK to have a misogynist, xenophobic, racist Islamophobic, republican candidate running for President of The United States!'

Terrorism? New York Governor Alexander Cuomo (center) described the bombs as 'terrorism.' Shortly after the explosion, a male 911 caller told an operator that 'There will be more'

The writer also decried 'all Republicans' as being 'cisgendered privileged white people.'

It concluded: 'This is not the end, this is just the beginning. I will be remembered. I will make a difference. I will eliminate my targets before it is too late.'

This was not the only time someone threatened more explosions in relation to the Chelsea bombings.

Shortly after the explosion occurred at 8.30pm, an unnamed male called 911 and said: 'I'm looking at the explosion down the block. There will be more.'

Investigators are 'vetting' the Tumblr page, NY Post reported.

If the manifesto is legitimate then the bomber chose a poor place for their tests; New York has one of the highest proportions of openly gay people in the US.

And according to a 2011 Huffington Post report, the majority of New York's gay population is clustered around the west side of Manhattan, with Chelsea firmly in the center.

In fact, that site said, The area between 6th and 8th Avenues, from West 18th to 22nd Streets, has the highest percentage of all, at 22 per cent.

The first explosion occurred on the corner of West 23rd Street and 6th Avenue, directly next to that area.