Canada Post's volunteer Santas will have to start making lists of the children they write to after at least 13 children in the Ottawa region received letters from "The North Pole" containing demeaning and insulting language.

The volunteers, who are current or former Canada Post employees, send a standard printed message and a personalized note responding to children who have written letters to Santa Claus.

Volunteers must now log their own names and the name of the child they are writing to, the company announced in a news release Friday. A permanent logging and tracking process will be included in the program next year.

'One or two Grinches can't stop Christmas from arriving, or Santa's letters being delivered.'— Cindy Daoust, Canada Post

The company received nine complaints Thursday about letters containing inappropriate language. Four more were discovered Friday, and one more letter containing inappropriate language was found at a local sorting plant.

Canada Post is urging parents to open letters from Santa themselves before their children can do so. The delivery of Santa letters has been temporarily suspended while the company searches for other inappropriate Santa letters that might still be in the postal system.

In addition, Canada Post is asking more of its employees to volunteer for the program so "Santa" can respond in time for Christmas despite the problems that have slowed the response process.

"One or two Grinches can't stop Christmas from arriving, or Santa's letters being delivered," program manager Cindy Daoust said in a statement.

Meanwhile, Ottawa police confirmed Thursday that they are investigating the complaints.

Daoust told CBC News the content that sparked complaints ranged from "inappropriate language and observations about the child's letter to Santa to more disturbing comments."

She said some of the letters were sent to younger children whose parents opened the letters, but a few were opened by children.

"We've spoken to a lot of these parents and expressed our dismay," she said. "We are devastated over this."

She added that there has never been a similar incident in the 26 years that the program has been running.

Canada Post issued a news release Thursday announcing that it would stop delivering the letters for at least two days and was making changes to its system for responding to the Santa letters to ensure this kind of thing doesn't happen again.