India's federal investigating agency on Tuesday arrested another five executives as it swooped down on companies run by two main suspects in an alleged $1.8 billion bank fraud case that continued for six years.

India's federal investigating agency on Tuesday arrested another five executives as it swooped down on companies run by two main suspects in an alleged $1.8 billion bank fraud case that continued for six years.

Vipul Ambani, president (finance) of Firestar International, Kavita Mankikar, authorised signatory of Firestar, Kapil Khandelwal, chief financial officer of Nakshatra and Gitanjali group, Arjun Patil, a senior executive in Firestar and Niten Shahi, a manager in Gitanjali group were all arrested Tuesday after several hours of questioning. They will be produced in a CBI court in Mumbai on Wednesday.

Central Bureau of Investigation spokesman Abhished Dayal said the five worked for the companies owned by Nirav Modi, a billionaire jeweller, and his uncle Mehul Chinubhai Choksi. Their whereabouts are not known although television stations are reporting that Nirav Modi has been spotted at a luxe hotel in New York's uptown Manhattan.

Meanwhile, more bad news for PNB: Rating agency Moody's has put the bank under review for a downgrade as concerns deepen around the multi billion fraud that hit the headlines last week.

Five bank executives and another employee of Modi's company Firestar group were arrested over the past three days for allegedly conspiring to cheat the state-owned Punjab National Bank, bringing the total number to 11, the spokesman said.

Modi allegedly cheated the bank by using fake bank "letters of understanding" to get loans. Most of the letters were sent to overseas offices of Indian banks, which made the actual loans, said Sunil Mehta, Punjab National Bank's managing director.

India's finance minister Arun Jaitley on Tuesday blamed bank management and auditors.

Such scams, he said, not only had a direct cost on the country and the taxpayers, but also an indirect cost on borrowings and development.

PTI reported that Modi sent a letter to the bank this week saying he owes less than half the amount claimed by the bank in connection with the alleged fraud.

Nirav runs an international jewelry empire that reaches from India to New York, with a string of high-end brands. He and his family fled India weeks before the bank registered a criminal case with the CBI on Jan. 31.

The CBI and other Indian investigative agencies searched dozens of offices and residences used by Modi and his business partners. The bank named Modi, his brother Nishal Modi, wife Ami Modi and uncle Mehul Chinubhai Choksi as suspects in its complaint.

In his letter to the bank, Modi said he owes about 50 billion rupees ($775 million), according to PTI. He said the $1.8 billion cited by the bank had resulted in a media frenzy that pressured authorities to quickly search and seize assets from his Firestar International and Firestar Diamond International companies.

"This thereby jeopardized our ability to discharge the dues of the group to the banks," Modi said.

The CBI spokesman said the agency had not yet received Modi's letter. There was no immediate comment from the state-run bank.

With the Indian media reporting that Modi and his family were hiding in New York or Dubai, the External Affairs Ministry said it has suspended the passports of Modi and his uncle, Choksi, for four weeks.

It said in a statement that if they fail to explain within seven days why their passports should not be canceled, their travel documents will be revoked.

With inputs from AP