LONDON (AP) _ The rogue trader who busted Britain's oldest investment bank was detected when he ran out of money in Singapore and beseeched the home office for more, a central government banking source said Tuesday.

Executives at Baring Brothers & Co. in London, who until last week were held in high esteem for their investment savvy, thought there was something irregular about Nick Leeson's request.

So they flew an accountant to Singapore, where the problems that had brought the bank to ruin quickly became apparent, said the source at the Bank of England.

Barings bosses were stupefied to learn that Leeson, a 28-year-old Englishman who ran the bank's Singapore futures trading desk, had lost hundreds of millions of dollars by wrongly betting that the Tokyo stock market would rise.

As the Nikkei 225 index of key Tokyo stocks kept falling, the Singapore International Monetary Exchange made nightly ``margin calls,'' or demands for Barings to write checks to cover its rising losses.

``The guy was getting more and more margin calls,'' said the Bank of England source, speaking on condition of anonymity. ``He used up the local kitty. He had to ask London for money to make margin calls. Rather puzzled, they sent an accountant out there to make the numbers add up.''

The numbers didn't add up. Over the weekend Barings was placed under the control of court-appointed administrators, the British equivalent of bankruptcy protection, marking one of the most spectacular financial downfalls in British investment banking.

The administrators, from the accounting firm of Ernst & Young, remained silent Tuesday about their efforts to unravel the problems at Barings and find buyers for all or parts of the bank.

Barings did not return telephone calls Tuesday.

Without question the administrators have a tricky job because they need to act quickly to keep Barings going as a viable business without seeing its talented staff depart. But acting too fast will be impossible because the Barings business is complex and getting a handle on the troubles caused by Leeson could be difficult.

A weekend attempt to rescue the bank failed because other bankers balked over the inability to get firm numbers for the losses at Barings.

Regulators have said the losses are at least $1 billion, but that sum could fluctuate depending on how administrators have acted in resolving the risky futures contracts purchased by Leeson on the Singapore exchange.

Over the weekend, the Barings contracts were still open. That means losses could have mounted Monday, when Tokyo stocks fell, or lessened Tuesday, when Tokyo stocks rose, unless Barings was out of the market by then. The administrators have refused to tip their hand on this question.

``Until we know the full extent of the damage, the administrators have no way of knowing what they need to sell,'' said Johnny de la Hay, who follows investment banks for Societe Generale Strauss Turnbull in London. ``We're already hearing news of people leaving, and if they don't get this done, there's nothing left, both in terms of staff and clientele.''

Although Barings was open for business in the United States, its office operations elsewhere around the world were paralyzed, bankers said. The administrators were unable to say immediately Tuesday just what was working at Barings and what wasn't.

De la Hay said that unless administrators are quick about putting Barings under new ownership, either by selling it whole or in parts, clients will abandon Barings for the simplest of reasons: ``If you want a deal done, they can't do it.''

Although banking regulators have started to assemble details of Leeson's astonishing trail of trading, no one has yet come up with a firm motive.

Leeson disappeared from his luxury home in Singapore on Thursday as the trading fiasco became apparent to Barings. He was last known to have been in Kuala Lumpur, the Malaysian capital, where he checked out of a hotel on Friday. Police in Malaysia said Tuesday they were looking for him.

In Singapore, commercial affairs department investigators spent 40 minutes searching Leeson's condominium apartment on Tuesday, witnesses said.

Barings has lodged a complaint with the commercial affairs department in Singapore. A department spokeswoman refused to give details of the complaint or say whether it was against Leeson.

Such a complaint would allow Singapore authorities to detain anyone they believed was involved, or to ask other countries to arrest people implicated in the case.