By Jesse Drucker
The Wall Street Journal

Senate investigators, ratcheting up the pressure on corporate tax-cutting transactions, have sent letters to at least 30 companies seeking details of past tax arrangements.

Companies that have received such letters include Merck & Co., Johnson & Johnson and Wyeth, according to a person familiar with the matter. Representatives for Merck and Johnson & Johnson said the companies were in the process of responding to the Senate request. A Wyeth spokesman wouldn’t comment.

The probe, by the Senate’s Permanent Subcommittee on Investigations, appears to have been sparked by an accounting rule known as FIN 48, which took effect in January.