Proskauer Rose, Debevoise & Plimpton and Ropes & Gray have added lawyers in the city since Beijing started its bribery probe of GlaxoSmithKline and US investigations of jobs given to the children of government officials by banks began.

"Hong Kong and Asia weren't traditionally seen as a hot spot for US litigators," said Bradley Klein, an investigations lawyer with Skadden, Arps, Slate, Meagher & Flom who moved to Beijing from Washington two years ago before moving to Hong Kong. "In the last three to five years, that's changed completely."

The Glaxo case was a wake-up call for global companies that assumed their main regulatory risk was in their home country, Klein said. "This opened up a new front and the risk of having to juggle multiple investigations in multiple jurisdictions," he said.

China fined Glaxo US$489 million last month for bribing doctors to help sales of its drugs after an investigation that lasted almost 15 months. The fine was the biggest corporate penalty ever in the country, Xinhua said.

"The Chinese Communist Party … is fighting for its survival and credibility by cleaning up," said Martin Rogers, who joined Davis Polk & Wardwell in Hong Kong last year. "This is at least a medium-term anti-corruption campaign which will involve more and more international companies."

The party's Central Committee is meeting this week and may establish an agency to institutionalise the anti-graft campaign, according to Chinese legal scholars. The investigation of whether Wall Street's hiring practices violated US anti-bribery laws has expanded in another direction.

The Independent Commission Against Corruption has opened a probe and interviewed JP Morgan bankers, who have needed individual legal counsel.

Davis Polk was advising five global banks on issues related to their hiring practices and the work was expected to continue at least into next year, Rogers said.

The firm is also advising state-owned companies on improving their anti-graft compliance and investigations procedures.

Davis Polk would expand its 25-lawyer disputes team in Asia with as many as 10 lawyers over the next five years, Rogers said.

It is a complex cocktail, according to Matthew Newick, who moved to Hong Kong from London to succeed Rogers as head of Asian litigation and dispute resolution at Clifford Chance.

"Companies which want to avoid investigations are increasing investment in compliance," said Andrew Dale, a white collar and corporate investigations partner at Orrick, Herrington & Sutcliffe.

"There can be a long tail to this kind of enforcement action," said Wilson Ang, a Singapore-based regulatory compliance and investigations partner of Norton Rose Fulbright. Cases can be followed by civil actions against directors and management, "then possibly insolvency proceedings if the company goes under".

For large investigations, there is a huge amount of time-sensitive heavy lifting to be done in Asia and in-house lawyers face additional pressure if their external lawyers have to fly in from the US or Britain, according to Julia Gorham, who joined DLA Piper in May from JP Morgan.

While the field is getting more crowded, established lawyers like Tham Yuet Ming of Sidley Austin, a former Singapore prosecutor and internal lawyer for Pfizer, say there is plenty of work at the moment. "I've barely had a weekend off for the last eight months," Tham said.