LONDON, July 19: British police said on Sunday they had launched an inquiry into how a secret police dossier went missing that according to a newspaper report contained counter-terrorist plans for London's Heathrow airport.

The dossier, found lying on a road, showed 62 sites at the airport where Al Qaeda was most likely to launch anti-aircraft missile strikes, the Sun newspaper said in its Monday edition.

It said the dossier included facts about surveillance, escape routes, evacuation plans and deployment of rooftop snipers at the world's busiest international hub. The plans, which have since been returned to police, were found by a motorist, the newspaper said.

A police spokeswoman said: "We treat any breach of security extremely seriously." "We have launched an internal inquiry into the circumstances of how these documents went missing and will take the appropriate action when we have ascertained the facts surrounding this matter," she added

She could not confirm whether the dossier was compiled by the SO18 anti-terrorist Aviation Security team, which is based at Heathrow police station. According to The Sun, the papers contained detailed maps and photographs, including aerial and satellite shots.

In one section, the dossier identified a field close to the airport as being ideal for a terrorist attack. "This site affords an excellent site to attack aircraft departing Heathrow," it quoted from the dossier, saying it included aerial and satellite photographs of the site.

Dated June 26 2004, the dossier gave surveillance and assessment information valid until December, the newspaper said. Ten years ago, the Irish Republican Army targeted Heathrow airport with rocket attacks. None of the missiles packed with Semtex plastic explosive detonated.

Security chiefs sent tanks into Heathrow last year after intelligence pointed to a threatened missile attack. This year, flights to the US have been cancelled amid fears of an al Qaeda attack. -Reuters