Ambulance workers were forced to scramble in their pockets for money to pay a $130 (£88) bill for three cases of water used to treat victims for shock after the twin towers collapsed.

Orin Smith, president of the Seattle-based coffee chain, sent a refund and free coffee to the ambulance crew after the incident was revealed.

"It's totally inconsistent with the kind of behaviour we would have expected from our people, so it has been very upsetting to learn of this," Mr Smith said.

He added that he did not know why the coffee shop in Battery Park Plaza, near the scene of the attack, had charged for the water.

Al Rapisarda, president of Midwood Ambulance Service, whose workers had to come up with the cash, said he had been personally called by Mr Smith to apologise for the outlet's actions.

"It was a misunderstanding with Starbucks," said Mr Rapisarda.

"It's not a big deal anymore."

The manager of the shop refused to comment.

Starbucks closed stores across America on the day after the attacks, although several premises close to the World Trade Centre and New York hospitals served coffee - and water - to rescue workers for free.