British drug maker AstraZeneca PLC, facing generic competition for some of its biggest products, says first-quarter profits fell 31 percent.

The company also announced Thursday that it has received a subpoena from legal authorities in Massachusetts.

Net profit for the three months to March 31 was $1.01 billion, down from $1.63 billion a year earlier.

Revenue was 13 percent lower at $6.39 billion. The company said generic competition for bipolar medication Seroquel IR, hypertension drug Atacand and cholesterol drug Crestor drove revenue down.

The company said it received a subpoena March 28 from the U.S. attorney’s office in Boston seeking documents relating to standards at its facility in Macclesfield, northwest England. It did not give further details.

AstraZeneca shares fell 1.8 percent to 33.28 pounds on the London Stock Exchange.