A former Riggs Bank manager yesterday invoked the Fifth Amendment and refused to answer questions from a Senate panel investigating his handling of hundreds of millions of dollars in suspicious transactions for a West African dictator, including why he lugged a 60-pound suitcase stuffed with $3 million in plastic-wrapped cash to Riggs's Dupont Circle branch.

The Senate probe is the latest in a series of investigations into Riggs's once-prestigious embassy banking division, now tarnished by reports that it helped former Chilean dictator Augusto Pinochet hide millions and that it appears to have allowed its biggest customer, Equatorial Guinea, and that country's president, Teodoro Obiang Nguema, to siphon oil revenue into his personal accounts. Despite the fact Obiang and his wife made cash deposits of nearly $13 million over a three-year period into their Riggs accounts, the bank never filed a single suspicious activity report to federal regulators as required by law.

The Senate permanent subcommittee on investigations called four current and former Riggs executives to testify yesterday, after releasing the results of its year-long probe into the bank. Simon P. Kareri, who managed Riggs's West African business until he was fired in January, was the only executive to assert his right not to testify against himself.

As details unfolded about the relationship of Riggs and Obiang -- whose government has been under scrutiny by international watchdog organizations for corruption and human rights abuses, Sen. Carl M. Levin (D-Mich.), the ranking minority member whose staff conducted the investigation, leaned over and removed his glasses as he pointedly asked Riggs President Lawrence I. Hebert how he could live with himself.

Referring to a letter sent to Obiang after Riggs officials entertained him at a luncheon at the bank, Levin asked: "How do you write that stuff to a guy who's as abominable as this guy? And knowing that he's abominable?"

Obiang had "a significant amount of money in the bank," Hebert replied, defending the deferential language in the letter, which both he and Riggs Chairman Robert L. Allbritton had signed. "I wanted to see this person."

In addition to the subcommittee's inquiry into Riggs's dealings with Pinochet and Obiang, the full Senate Governmental Affairs Committee is conducting a separate review of the bank's dealings with the Embassy of Saudi Arabia. In May, Riggs was fined $25 million for repeated violations of laws designed to prevent money laundering, particularly in its dealings with the embassies of Saudi Arabia and Equatorial Guinea. Since then, the bank has retained investment bankers to explore a sale of the company.

The probe into Riggs reflects broader concerns in Congress and elsewhere that systems designed to detect suspicious financial transactions may not be adequate for a job that now includes preventing financing for terrorism.

Yesterday's hearing included lengthy questioning of R. Ashley Lee, who was hired by the bank as an executive vice president after retiring from his post as the federal bank examiner in charge of overseeing Riggs.

Levin pressed Lee on his actions as Riggs's examiner-in-charge from 1998 to 2002. Lee contradicted sworn affidavits from two former Riggs examiners under his supervision who told the committee that Lee instructed them to exclude documents detailing Riggs's relationship with Pinochet from a regulatory database. Lee yesterday denied ever giving the instruction.

"I don't remember instructing anyone to do this," Lee said.

Levin said contradictions between Lee's sworn testimony and that of other regulators warrant a review by the Justice Department to determine whether anyone lied. Subcommittee Chairman Norm Coleman (R-Minn.) said through a spokesman yesterday that he plans to refer the matter to the Justice Department to determine whether Lee broke any laws.

"The referral to the Justice Department is a matter for Ashley Lee to address, but what I can tell you is that Ashley Lee has been with Riggs since 2002 and we believe he has conducted himself in an honorable and ethical manner," Riggs spokesman Mark N. Hendrix said.

Yesterday's hearing was the first unscripted public accounting Riggs officials have provided about the growing scandal in its embassy banking division. The bank is shutting down that business.

Much of yesterday's hearing focused on Riggs's eight-year relationship with Equatorial Guinea, a profoundly poor country whose president has been cited by the State Department and various human rights organizations as among the most corrupt and brutal dictators in the world. Significant amounts of oil were discovered in Equatorial Guinea in the mid-1990s; since 1995 hundreds of millions of dollars in cash from U.S. oil companies poured into "the oil account" the country maintained at Riggs, at one point reaching $700 million. Much of the suspicious activity that was conducted at Riggs by Obiang, his family and other government officials involved this government account, Senate investigators found.

Equatorial Guinea had more than 60 accounts at Riggs. The oil account was the largest, acting as the virtual state treasury. About half of the 60 accounts were private bank accounts for the country's various ministers and their families, with millions of dollars, much of it in cash, moving in and out. All of it was managed by Kareri, the report states.

Riggs helped Obiang create Otong SA, a Bahamas-based company owned by him. From 2000 to 2002, Obiang deposited $11.5 million in cash into this account in increments of $1 million to $3 million. On at least two occasions, a bank employee told subcommittee investigators, Kareri would go to the embassy in Washington and bring back suitcases filled with up to $3 million in $100 bills.

Riggs also accepted cash deposits totaling $1.4 million into accounts held by Obiang's wife, Constancia Nsue. All of the cash deposits were accepted with "no questions asked," according to the subcommittee.

The subcommittee also heard testimony from three major oil companies on their substantial financial relationships with Equatorial Guinea: ExxonMobil Production Co., Amerada Hess Corp. and Marathon Oil Co. All three have oil operations in the country and often contracted, for security and other services, with companies in which the ruling family had an interest.

In addition to the oil account, Riggs managed several accounts funded by oil companies to pay tuition and expenses for Equatorial Guinean nationals studying abroad. Hundreds of thousands of dollars passed into and out of these accounts from 2001 to 2003 to more than 100 students, many of them relatives of the country's top officials.

The executives each said their companies' business relationships with Obiang and his family were not a quid pro quo for being able to extract the country's oil.

Eventually, Riggs hired a former Secret Service agent, David B. Caruso, as its chief compliance officer. Caruso conducted an investigation into the bank's Equatorial Guinea dealings and discovered more than $35 million had been wired out of the country's oil account from 1998 to 2002 to companies with accounts in "jurisdictions with bank secrecy laws." In other words, Riggs could not identify the destination of the money. Caruso set up a meeting with Equatorial Guinea officials, including Obiang, at the Four Seasons Hotel in Georgetown in February to ask about the transfers and other matters. Equatorial Guinea officials declined to answer questions. Soon after, Riggs asked Equatorial Guinea officials to close all their accounts at Riggs.

Kareri had been fired a month earlier, after the bank began questioning him about a $140,000 check made out to a friend of Kareri's by Obiang's son. Investigators at the bank also later discovered that more than $1 million had been transferred out of the oil account to an offshore company controlled by Kareri's wife. According to the Senate report, Kareri "abruptly left the United States and went to EG in January 2004. During his absence, the bank initially suspended and then fired him."

A source familiar with the subcommittee investigations said Kareri returned on his own to the United States. A grand jury in the District is focusing on Riggs's relationship with Equatorial Guinea and is still gathering documents, according to a federal official who spoke on condition of anonymity.

None of the transactions detailed in the report generated suspicious activity reports to law enforcement at the time they were made. Hebert attributed this to the domination of Kareri over the relationship and the lack of internal systems designed to track and identify suspicious transactions.

"I was not aware that they were bringing that amount of cash into the bank," Hebert said, admitting that proper procedures were not followed in the Equatorial Guinea relationship. "[Anti-money-laundering] compliance was a challenge for this bank."

Riggs National Corp., the bank's holding company, is considering offers to buy the bank. Cleveland's National City Corp., Pittsburgh's PNC Financial Services Group Inc., Mercantile Bankshares Corp. of Baltimore, and M&T Bank Corp. of Buffalo all have expressed interest, according to a source close to the negotiations who asked not to be identified because of ongoing talks.

Riggs's stock price closed yesterday at $22.67, up 17 cents, as investors anticipate its likely sale. Riggs is scheduled to release second-quarter results next week.

Former and current Riggs executives Simon P. Kareri, from left, Lawrence I. Hebert, Raymond M. Lund and R. Ashley Lee were called to testify.Simon Kareri was in charge of the money from Equatorial Guinea.Riggs President Lawrence I. Hebert said procedures weren't followed.