British Airways is trying to contact 33,000 passengers after radioactive traces were found on two of its planes.

A third plane, currently in Moscow, is to be flown back to the UK for tests.

The low grade radiation was found by scientists investigating the death of ex-spy Alexander Litvinenko. An inquest into the death opens later on Thursday.

BA has named 221 affected flights on its website and passengers are urged to contact NHS Direct or their own doctor. The health risk is thought to be low.

A spokeswoman for BA said the airline had also been "proactively calling passengers" and hoped to have contacted the majority by the end of Thursday.

It has so far taken calls from 2,500 customers on a dedicated helpline.

An estimated 3,000 staff would also need to be checked, BA said.

The alert involves 221 flights made by the three short-haul 767s in Europe between 25 October and 29 November, almost a quarter of which were between Moscow and London.

Tracing movements

Mr Litvinenko, an ex-KGB agent and a fierce critic of Russian president Vladimir Putin, died last week of radiation poisoning.