The fax, which the zoo received on Wednesday read, "Knut is dead. Thursday noon."

Zoo officials immediately alerted police who inspected the enclosure where Knut, who was rejected by his mother at birth and was raised by zookeepers, makes daily appearances before packed crowds.

Police spokesman Michael Maass dismissed the threat. He denied a report in Germany's mass-circulation Bild, which has followed Knut on its front page since his Dec. 5 birth at the zoo, that the cub was under police protection.

"However, we will send officers over to the zoo later today to make sure everything is all right," Maass said, adding there would be heightened security because German President Horst Koehler is scheduled to open an exhibit there later Thursday.

A spokeswoman for the zoo said a regular group of security guards watch over the celebrity cub, but declined to elaborate other than to say the fax wouldn’t change his schedule.

"Our two daily public viewings of Knut will not be canceled because of the death fax," zoo spokeswoman Vivian Kreft said.

Thousands of people line up each day to see Knut, attracting as many as 15,000 people to the zoo daily. He also has his own blog and TV show and appeared on the cover of Vanity Fair.

Knut caused his fans to worry earlier this week, when his daily shows were canceled because he appeared weak and had to be given medication.

His twice-daily hour-long appearances resumed after a one-day break to recover from teething pains.