Nirav Modi is a billionaire jeweler whose luxury stores and boutiques are located in New York, Hong Kong, Macau and India. He is being investigated in connection with a $1.8 billion bank fraud in India.

Indian firm Cyril Amarchand Mangaldas, the largest law firm in India, was raided in late February by government authorities in connection with one of the largest cases of bank fraud in the country, according to media reports.

The Central Bureau of Investigation of India—the nation’s equivalent of the FBI in the United States—visited Cyril Amarchand’s head office in Mumbai last week and took documents related to firm client Nirav Modi, a billionaire jeweler, local press outlets Legally India and Bar & Bench reported.

The raid raised concerns in the legal community over attorney-client privilege.

In January, Punjab National Bank reported to the CBI that companies controlled by Modi and his family had used fraudulent bank guarantees to gain credit worth $1.77 billion. Jeweler traders controlled by Modi and his uncle, Mehul Choksi, allegedly paid off PNB employees to issue fraudulent letters of undertakings to several banks in Hong Kong and elsewhere in order to gain short-term credit overseas. Punjab National Bank is liable for the credit in the case of default.

Cyril Amarchand, India’s largest law firm by lawyer head count, was reportedly engaged by Modi for a banking-related mandate shortly before news of the alleged fraud broke in mid-February. The firm had not worked for Modi before, according to Legally India and Bar & Bench, and it terminated its relationship on the banking matter once allegations against Modi were reported.

The 619-lawyer Mumbai-based law firm was created in 2015 by managing partner Cyril Shroff after splitting from the legacy firm Amarchand & Mangaldas & Suresh A. Shroff & Co. and his older brother Shardul Shroff. The brothers, once co-managing partners of the 800-lawyer legacy firm, went separate ways nearly three years ago after unsuccessful efforts to resolve a dispute over their late mother’s estate.

The CBI’s collecting of Modi-related documents at Cyril Amarchand’s office also raised concerns over attorney-client privilege among the legal community. The Indian Evidence Act does protect confidential communications between a client and a lawyer, but disclosure of privileged communications made for illegal purposes or in committing a crime or fraud is allowed under the law.

A Mumbai-based lawyer not connected to the firm said that without knowledge of the case and details of CBI’s process, it’s difficult to judge whether attorney-client privilege was breached. But he noted that lawyers in India walk a fine line between breaching attorney-client privilege and being accused of obstructing justice by law enforcement. “Firms ought to be more careful in taking on clients,” he said.

Cyril Amarchand did not respond to requests for comment.