MINNEAPOLIS (AP) _ Police skirmished with protesters Monday near a downtown hotel where an international conference of scientists had convened to discuss the latest advances in animal genetics.

Eighty people were arrested, Police Chief Robert Olson said. One police officer suffered a minor injury; no major injuries were reported among protesters, though dozens were sprayed with pepper spray and others were struck with police batons.

``We tried to be as gentle as we could,'' Olson said. ``They want to shut down our city. We were not going to let them do that.''

The skirmishes were the first significant disruption since the International Society for Animal Genetics conference opened Friday under heavy security.

Police also said Monday night that canisters left by activists at a McDonald's restaurant and at least one other location contained traces of cyanide. FBI tests revealed the presence of the poison, which is lethal when inhaled or digested.

``I don't wanna be starting any panic thing, but this is clearly ratcheted up, at least on the side of the protests. And this is clearly connected to that,'' Olson said.

Police, determined to avoid violence on the scale of the WTO protests in Seattle last year, erected concrete barriers and steel fencing around the hotel, where about 650 scientists are meeting through Wednesday.

Monday's scuffles broke out after more than 200 protesters had gathered in a downtown park. About 1 p.m., a group of about 25 tested a line of about 12 officers in riot gear about three blocks from the hotel.

When the protesters tried to break through, they and at least two news photographers were wrestled to the ground by police.

A gas canister apparently containing a chemical irritant was deployed by protesters, who also threw rocks at officers, said Roseann Campagnoli, a spokeswoman for the Hennepin County Sheriff's Department and Deputy Police Chief G.S. Hestness.

Officers fired what Hestness described as rubber batons _ beanbag-like projectiles _ into the crowd.

Eventually, protesters did break through a police line into a second park, which has served as a staging area for demonstrators since the meeting opening Friday evening. Officers fired pepper spray into the crowd, Campagnoli said.

By mid-afternoon, she said, activities had ``cooled down considerably.''

ISAG is one of the world's most prominent groups that shares information on the gene mapping of livestock and companion animals, used to enhance their health and resistance to disease.

Activists say genetic engineering threatens biodiversity and could pollute delicate ecosystems, or create a society in which corporations and the government control what kinds of animals and humans are born.