Officials already have DNA evidence that suggests the fish has made it past the area's electric fish barriers. Now, they're looking for actual fish.
Crews are focusing on areas where warm water from industrial operations enters the waterways. That's because fish tend to congregate near the warmer water in the winter.
Crews will use commercial fishing nets and electrofishing to search over the next two to three weeks. They put up the nets Wednesday.
In December, officials discovered a single carp in a canal leading to Lake Michigan, the closest the species has been found to the Great Lakes.
Environmentalists fear invasive carp could endanger the lakes' $7 billion-a-year fishing industry.