A judge in Corpus Christi, Tex., yesterday asked the district attorney to investigate after Bayer sent thousands of letters to residents before jury selection in a lawsuit involving its anticholesterol drug, Baycol.

Judge James B. Klager of Nueces County Court called Bayer's mailing of the letters "outlandish" and said there were concerns that it might constitute an attempt to tamper with the jury.

"I just cannot let this sort of thing occur," Judge Klager said. Bayer, the giant drug company based in Germany, called the mailing a mistake and apologized to the court.

The judge agreed thatthe trial could continue, but said he would hold a hearing on possible sanctions after the trial concluded.

The case in Corpus Christi is the first of thousands involving Baycol to go to trial. More than 10,000 patients have filed lawsuits against Bayer, which pulled the drug in 2001 because it can cause a rare, sometimes fatal, muscle disorder. Bayer has said about 100 deaths have been linked to the drug. Bayer sent the two-page letters on Monday, the day before jury selection was to begin. In them, Bayer described its position in the case and noted that it employs nearly 2,000 people at several Texas operations.

It asked the recipient to "keep an open mind" about the drug company. Two people who were considered as jurors received the Bayer letters but not until after they were dismissed. Judge Klager said that the chosen jurors could continue.

Philip S. Beck, a lawyer for Bayer, said the company's public relations executives sent the letter because they were concerned about publicity that might be generated during the trial by lawyers for Hollis W. Haltom, the 82-year-old patient who filed the lawsuit. The letter was intended for members of the Corpus Christi Chamber of Commerce, he said, but "a miscommunication" caused it to be sent to 2,100 people.

"We apologized to the court," Mr. Beck said, "because we made a mistake." The letter states that Bayer took "immediate and appropriate action" to tell doctors about Baycol's potential side effects.

The letter also says that Bayer had tried to reach a "fair settlement" with Mr. Haltom, but his lawyers turned it down. It is signed by Meredith B. Fischer, vice president for communications and public policy for Bayer's health care operations in North America.

"As you hear and see reports of the trial, I hope that you will keep an open mind to the efforts that Bayer made to give fair redress to this gentleman and, on a much broader scale, the tremendous contributions that our company has and continues to make to the health and welfare of millions of people worldwide," Ms. Fischer wrote.