Four Firms Added to U.S. Stock-Option Probe

Four companies, including Analog Devices Inc. and online publisher Cnet Networks Inc., said they had become subjects of the U.S. government’s investigation into the backdating of stock-option grants.

Computer chip makers Analog Devices and Power Integrations Inc. said they had received subpoenas from federal prosecutors. Cnet, the online publisher of technology news, and biopharmaceutical company Medarex Inc. said the Securities and Exchange Commission began informal probes.

At least 23 companies are under federal scrutiny over whether they deliberately moved option grants back to dates when their stock price was lower to benefit executives.

Analog Devices fell 25 cents to $33.39, and Medarex dropped 26 cents to $10.60. Cnet rose a penny to $9.18 and Power Integrations rose 15 cents to $17.50.