Three of the injured were airlifted from the crash site and all seven were taken to area hospitals, she said.
Hill was not sure whether those on the Crownline boat were tossed into the water during the crash.
She said it doesn't appear anyone was aboard the 25-foot tug boat, which is registered to F&A Enterprises in St. Augustine.
The victims' names have not been released. Hill said investigators were still trying to verify their identities.
"Investigators are looking at anything that may have caused this," Hill said, including the speed and capacity of the boat, lighting conditions and whether alcohol may have been a factor.
The boat was carrying 12 people, according to Jeremy Robshaw of the St. Johns County Fire and Rescue. He told The Florida Times-Union newspaper that three of those injured were in critical condition, with the others in stable condition.
Robshaw said the pier was under construction and rescuers had to lay down planking before they could get to the crash victims.
Herb Davis watched the rescue from the dock at his home down the street.
"There was a lot of moaning," he told the newspaper. "It was very clear, this lady was screaming so loud," he said.
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