Singapore's anti-graft bureau, the Corrupt Practices Investigation Bureau (CPIB), said on Friday that the country's transport minister Subramaniam Iswaran and hotel tycoon Ong Beng Seng were released on bail in a rare top-level corruption probe.

The two were arrested on the same day and released on bail in connection with the investigation, the bureau said without further disclosing details of the probe.

Singapore is a country well-reputed for being among the least corrupt countries in the world. As a means of deterring corruption, the government pays its ministers wages nearly similar to those of top earners in the private sector.

Ong, a tycoon hotelier, is the managing director of Hotel Properties Limited (HPL). The company said in a Friday filing with the Singapore Exchange that Ong has been asked by the CPIB to provide information about his interactions with Iswaran.

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Although the passports of those under arrest are generally confiscated, Ong was given permission to travel overseas, with the bureau noting that it considers such requests "on a case-by-case basis."

However, given his request, the bureau has increased his bail to Sg$100,000 ($76,000).

"Upon his return, Ong is required to report to CPIB and surrender his passport to the bureau," the CPIB said.

As for Iswaran, the minister received orders from Prime Minister Lee Hsien Loong to go on leave earlier this week.

Several other people are currently being investigated in the anti-graft probe, according to reports. 

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