In the face of anti-trust opposition, 3M Co. and Avery-Dennison Corp. said late Wednesday that they had terminated an agreement for 3M to buy Avery-Dennison’s office and consumer products business.

The Justice Department last month threatened to sue to block the $550 million deal, citing concerns that the addition of the Brea-based unit – which makes Marks-A-Lot pens, binders and other office materials – would give an unfair advantage to the St. Paul, Minn. technology and consumer products giant, whose products include Post-It notes and Scotch Tape.

Pasadena-based Avery-Dennison, which had hoped to divest the office products unit in order to focus on its label and sign business, said after the markets closed that it would look for another buyer for the office products business.

Shares, which earlier closed down 36 cents, or 1 percent, to $31.45 on the New York Stock Exchange, fell another 7.5 percent in after-hours trading.