Hedge fund manager Leon Cooperman said regulators are considering taking action against him and his firm Omega Advisors over trading in certain securities, according to a person familiar with the matter.

Cooperman told clients in a letter dated March 21 that he and his firm received a Wells notice regarding an investment in a single issuer that it had since 2007, said the person, asking not to be identified because the information isn’t public. Regulators are looking at trading in the security in 2010, the investor wrote, according to the person.

Cooperman, 72, declined to comment on the Wells notice when reached by phone, as did Ryan White, a spokesman for the U.S. Securities and Exchange Commission.

The SEC sends a Wells notice to a company or an individual after its staff has determined that sufficient wrongdoing has occurred to warrant civil claims being filed. Cooperman told clients about a year ago that his firm was subpoenaed by the SEC and the U.S. Attorney’s Office in New Jersey over trading in certain securities.

Cooperman told clients in the letter Monday that he’d been asked to speak with regulators on March 11 and had declined at the advice of his lawyers, invoking his Fifth Amendment right not to incriminate himself.

Losing Years

He added that the firm strongly disagreed with regulators that it had violated securities laws, according to the person. Cooperman said that the notice also covered trading in the same issuer by a third party.

Omega, based in New York, returned an annual average of 11 percent from inception in 1991 through 2014, according to an investor letter. After Omega declined 2.8 percent in 2014, Cooperman said he was embarrassed by the losses. Performance has gotten worse since then. The fund lost 10.4 percent in 2015 and was down 10 percent in the first two months of 2016.

The Wells notice comes as the U.S. investigates wrongdoing on Wall Street, including a multi-year crackdown on insider trading. Some of the government’s early victories in that effort have recently been overturned in court.

Cooperman is a regular guest on financial news television and speaks frequently at investment conferences. He is the son of a plumber and learned to analyze securities from the late Roger Murray, a professor at Columbia Business School, where Cooperman graduated. He went on to spend 25 years at Goldman Sachs Group Inc. before starting Omega in 1991.