Large clouds of black smoke billowed after two disused water towers near the National Archives in Kew, London was said to be on fire.
The main building, which was open to the public, was evacuated after the blaze broke out, a National Archives spokeswoman said.
Footage of a fire near the National Archives in Kew, London has been pictured by locals around the area. Tom Hewitson, who filmed the footage, said that a "smaller building on the side" was affected.
A blaze near the National Archives in Kew, London has been pictured by locals around the area. Thick black smoke could be seen from Chiswick Bridge.
National Archives later said the fire had been put out and that records were safe and unharmed.
Fire at National Archives (Kew) as seen from Chiswick Bridge on my run this morning. http://t.co/eSxOWRu0FJ
A blaze near the National Archives in London caused "significant damage" to two water towers close to the area, London Fire Brigade said in a statement.
The rescue service added:
Crews tackled the blaze, which was affecting two disused water towers, and brought the fire under control quickly. No injuries were reported. The fire caused significant damage to the water towers and smoke could be seen from the surrounding area.
The cause of the fire is under investigation.
Around 20 firefighters are tackling a blaze close to the National Archives. London Fire Brigade said two disused water towers which were in the process of being decommissioned caught fire in Kew, south west London, at about 12.30pm.
Both towers are now "100% alight", a fire service spokeswoman said. A Scotland Yard spokesman said: "No-one is trapped or injured."
Police, who were called at 12.37pm, are providing assistance at the scene, he added.
Libyan justice minister Salah al Marghani has said the country is offering Britain full transparency and help in bringing WPC Yvonne Fletcher's killer to justice.
"It is another crime of the Gaddafi regime and there is full cooperation in this case and we have 100 per cent open lines with the UK on these issues," Mr al Marghani said.
Newly released government files have shown Libya twice warned the UK of potential violence on the eve of the shooting of Ms Fletcher outside the Libyan People's Bureau in London in 1984.
The gunman who fired the fatal shot from inside the embassy has never been identified.
The former British ambassador in Tripoli has told ITV News he took a threat of violence on the eve of the shooting of WPc Yvonne Fletcher "seriously" after it was revealed he bet a Libyan diplomat that nothing would happen.
Oliver Miles was summoned to the Libyan foreign ministry shortly after midnight on April 17 1984 to receive a warning of possible violence if a planned demonstration by opponents of Colonel Gaddafi went ahead that day outside the Libyan People's Bureau in London.
Mr Miles filed a telegram to the Foreign Office (FCO) reporting the warning, one of a number of documents released under the 30-year rule by the National Archives.
Other papers show two officials from the People's Bureau also telephoned the FCO to express concern about the demonstration the next day.
"I did take it seriously and that's why I reported it to London," Mr Miles told ITV News. "I didn't know, of course, that there was going to be a shooting. I thought they were simply trying to have the demonstration stopped."
The man who has fought to find WPC Yvonne Fletcher's killer has told ITV News he is demanding answers after new details of Libyan warnings.Read the full story ›
Margaret Thatcher considered calling on troops at the height of the miners' strike amid fears union action could destroy her government, according to newly-declassified files.
Government papers from 1984, released by the National Archives, show ministers were so concerned at the outbreak of a national docks strike while the miners were still out, they considered declaring a state of emergency.
Plans were drawn up for thousands of service personnel to commandeer trucks to move vital supplies of food and coal around the country.
It is thought to be the closest Mrs Thatcher came to defeat in her battle with the miners but the scheme was never implements after the dockers' action petered out after less than two weeks.
As Prime Minister, Margaret Thatcher's immaculately coiffed blonde locks were as much a part of her image as her famous handbag - and newly-released government files show just how much time she spent keeping up appearances.
Her appointments diary for 1984, released by the National Archives, show that she had 118 hair appointments in the space of 12 months.
In June, when she was hosting world leaders at an economic summit in London she had hair appointments on five consecutive days.
The diary also confirms her reputation as a workaholic who found it difficult to relax.