Media playback is unsupported on your device Media caption Police are investigating the death, as Jean MacKenzie reports from Bexleyheath

A teenager believed to have taken so-called laughing gas at a party in south-east London has died.

The 18-year-old was taken to hospital after collapsing in a street in Abbey Wood, shortly after 23:15 BST on Saturday. He died two hours later.

The Metropolitan Police said he was believed to have been drinking alcohol as well as ingesting legal high nitrous oxide, also known as laughing gas.

Seventeen people in the UK died between 2006 and 2012 after taking the drug.

The teenager's next of kin have been informed.

Image copyright SALIX HOMES

"At this stage the death is being treated as unexplained pending the findings of the post-mortem," a Met spokesman said.

The government plans to ban the sale of legal highs, which would include nitrous oxide.

The gas - inhaled using a balloon - can make people feel relaxed, euphoric and giggly, which has led to its nickname.

But abusing nitrous oxide can lead to oxygen deprivation resulting in loss of blood pressure, fainting and heart attacks.

It is not illegal to be in possession of the gas, although it is prohibited from being sold in England and Wales to under-18s if there is a risk they will inhale it.

Image copyright PYMCA / Alamy

Nitrous oxide

Also know as whippits, laughing gas and hippy crack, nitrous oxide can be fatal when inhaled as it effectively replaces oxygen

Severe vitamin B deficiency can develop with heavy, regular use of nitrous oxide, which can also cause serious nerve damage

The gas is used legitimately to numb pain during medical procedures; to increase power output of engines; and in some aerosol cans, such as whipped cream

'Whenever I see anyone selling it I'll buy a few balloons'

Daniel, a 19-year-old railway worker says:

Image copyright Yui Mok/PA Image caption Nitrous oxide is sold in small canisters

"I take them at weekends, festivals and holidays.

I got into it when I saw someone selling it, so I tried it and I liked the feeling of it. I mainly do it during a night out, it just gives you a two minute buzz.

Some of my friends do it and some don't. I wouldn't say it leads to other drugs.

They're popular because they're cheap, they don't stay in your system and it only last a few minutes and you can't get in trouble for doing them.

I didn't think laughing gas was dangerous. I was shocked to be honest when that guy died. I think I would reconsider doing them in future."

'Should you intervene when your housemate becomes addicted to laughing gas?'

Emma, 22, is an office administrator from South Wales.

Image caption The balloons cost about 1-2 euros abroad and can be delivered to your door in the UK, Emma says

"I've seen people hurt themselves with laughing gas. They stand up and spin with balloons and I saw one person fall over and land on the steps and crack his glasses.

Some would do a 'double balloon' to hallucinate and a lot would pass out for a few moments.

My friend did it out of boredom stupidly. She did about 50 balloons in her bedroom.

You can buy them abroad for about 1-2 euros but in the UK they can be ordered over the phone and delivered to your house.

I don't think they're very safe because of the lack of oxygen and the burns you can get from the canister and the risk of falling over.

At least with alcohol you can see what you're doing. The gas clouds your vision though and you can't hear properly.

You see colours and there's almost a pulsing sound that comes with it. Seeing people's face after they've done it isn't nice either. I got suckered into doing it once but I never did it again."