Lehman to file claim vs Marubeni on Monday - source

By Alison Tudor and Yuko Inoue

TOKYO, March 31 (Reuters) - U.S. investment bank Lehman Brothers (LEH.N: Quote, Profile, Research, Stock Buzz) will file a lawsuit on Monday against Japanese trading house Marubeni Corp (8002.T: Quote, Profile, Research, Stock Buzz), saying it was defrauded of more than $355 million, a source with direct knowledge of the matter said.

Shares in Marubeni Corp (8002.T: Quote, Profile, Research, Stock Buzz), Japan's No.5 trading house, plunged 6 percent on Monday, although it argued its staff may also have been duped in the case.

The U.S. investment bank is trying to recover a loan to a fund headed by Asclepius Ltd -- a now-bankrupt unit of LTT Bio-Pharma Co (4566.T: Quote, Profile, Research, Stock Buzz) -- that was arranged through Marubeni staff.

Another person briefed on the matter told Reuters on Saturday Lehman had believed the money, supposedly to be used to finance medical leases, was backed by Marubeni.

"Meetings took place in Marubeni offices, there was no reason to believe anything was untoward," said the first source, who declined to be named because of the lawsuit, to be filed in the Tokyo District Court.

The bank believed Marubeni was shirking its obligations to pay back the money, the person said.

Marubeni, which fired two contract employees involved in the case on March 10, said the staff may have been manipulated by the former president of Asclepius, that Marubeni had not approved the leases and that police were investigating the case.

The trading house's shares fell as low as 718 yen on Monday, before recovering to 729 yen, down 6.2 percent. (Editing by Rodney Joyce)