UPPER PENINSULA -- A Michigan official says poachers have shot six gray wolves, five in the Upper Peninsula this year, after three consecutive years in which the number of illegal wolf killings in the U.P. has risen.

In 2007, there were four wolves poached, 2008 had seven killed, 2009 had 12 killed and 2010 resulted in 14 confirmed wolf kills.

Brian Roell, wolf coordinator for the Michigan Department of Natural Resources and Environment, says it's unclear whether the recent uptick represents a trend or a minor blip.  He says the number of poaching cases has fluctuated over the past decade.

Wolves were driven to virtual extinction in Michigan decades ago, but have rebounded.  A census taken in 2010 put their number at 557.

Roell says the population remains strong.  He says only a few wolves regularly prey on livestock and pets, but many people in the U.P. are frustrated by their limited ability to deal with them.

Out of the wolves killed this year, one was killed in Luce County, one in Chippewa County, and three in Mackinac County.

The Associated Press contributed to this article.