WASHINGTON - INVESTIGATORS on Tuesday scoured the wreckage of two commuter trains hunting for clues to the worst subway accident in Washington's history which killed nine people and injured some 80 others.

Metro officials said they still had no clue why one train plowed into the back of another on an above-ground section of the system's Red Line just at the start of Monday's evening rush hour.

CAIRO - OVERWHELMED by police and left with limited alternatives, Iranian demonstrators resorted on Tuesday to more subtle ways of challenging the outcome of the presidential election: holding up posters, shouting from rooftops and turning on car headlights.

But the restrained expressions of discontent appeared to be scattered as Iran's ruling clerics dealt the opposition new setbacks, making clear they have no intention of holding a new vote and setting up a special court to deal with hundreds of protesters arrested in more than a week of unrest.

JIUTEPEC (Mexico) - INDUSTRIALISED and developing nations are finding more common ground on climate change issues although significant disagreements remain, the top US environmental diplomat said on Tuesday after two days of high-level talks.

Negotiations over a new climate change treaty that would for the first time set targets for fast-growing developing nations have stalled in part over their demands that the richest countries make deep cuts in greenhouse gas emissions.