U.S. Treasury Department officials are urging the financial sector to address potential challenges in using cloud computing services, warning in a report on Wednesday that failure to do so could leave them and their customers vulnerable.

The risk was particularly acute for small and medium-sized financial institutions, the department said.

Deputy Secretary of the Treasury Wally Adeyemo said while “there is no question that providing consumers with secure and reliable financial services means greater demand for cloud-based technologies,” there needed to be “safe and effective migration” as banks and other financial companies adopt cloud services.

“Treasury found that cloud services could help financial institutions become more resilient and secure, but that there were some significant challenges that could detract from these benefits,” department officials wrote in their report assessing current cloud adoption in the financial industry.

Those issues include financial firms’ exposure to potential cyber incidents, an industry-wide reliance on a small number of cloud providers and a lack of technology workers able to help financial institutions deploy cloud services, among other challenges, department officials said.

Treasury officials recommended steps that could help the sector adopt cloud computing, adding that it “neither endorses nor discourages cloud service adoption by the sector.”

The department was establishing a working group to address the challenges raised in the report and said it would work with U.S. financial regulators, the industry and international partners to address the risks.

Technology companies that provide cloud computing services include Amazon Inc’s (AMZN.O) Amazon Web Services, Alphabet Inc’s (GOOGL.O) Google, Microsoft Corp (MSFT.O) and Oracle Corp (ORCL.N).