Canadian police are monitoring U.S. fishing boats which they say are blatantly violating quarantine laws on international waters.

There was short police chase on April 15 on the Detroit River in which Canadian police and Customs officers intercepted two boats on the Canadian side of the river as two other boats fled back to U.S. waters, the RCMP say.

“The marine operation was in response to public concerns about American fishing boats violating the Quarantine Act, the Customs Act and the Reopening of Ontario Act,” RCMP Cpl. Dmitri Malakhov said in a release. “Four charter fishing boats registered in the U.S., were observed operating on the Canadian side of the Detroit River.”

A joint operation, including the marine units of Windsor RCMP, Windsor Police, and the Canada Border Services agency (CBSA) gave chase and were able to intercept two of the fishing boats, as two others sped into U.S. waters.

“The fishing bots were escorted to a nearby port-of-entry and were subject to examination by CBSA officers,” the RCMP said.

Tickets were issued to ten people by Windsor Police under the Reopening of Ontario Act for a total of $8,800.

All ten were identified as U.S. citizens and were served with a notice of Direction to Return to the USA by the CBSA under the Immigration and Refugee Protection Act and the Quarantine Act.