BOULDER — University of Colorado police are investigating threatening e-mails with anti-evolution messages sent to professors at the Boulder campus.

Police Cmdr. Brad Wiesley said Friday the e-mails claim be from a religious group but investigators did not know whether more than one person was behind them.

He said the e-mails were considered threatening and made reference to killing people who back evolutionary theory. He said they contained no specific threat against any individuals.

Wiesley declined to provide any other the details of the messages. It was not immediately clear how many people received them.

“The bottom line is this is an age-old debate between evolution and creationism that someone has very strong opinions about,” he said.

Wiesley said some professors had been receiving critical e-mails for weeks, but the tone became more threatening last week.

Last weekend, someone slid anti-evolution materials under the doors of offices and laboratories of the Ecology and Evolutionary Biology Department, Wiesley said.

A Web site called “The Panda’s Thumb,” a forum for responding to critics of evolution, posted what it said were excerpts from some of the e-mails. The writer accuses professors who teach evolution of “being the source of every imaginable evil in our society.”

The e-mail mentions a pastor’s message about killing “the enemies of Christian society.”

“But I believe it is far more effective to take up a pen to kill the enemies of Truth,” the message states.

CU spokesman Bronson Hilliard told The Denver Post that excerpts on the site were “consistent” with e-mails sent to CU professors, but he couldn’t say whether they were exact copies.

According to the site, the writer compares the professors to child molesters and accuses one of “being a murderer of souls.”