JACKSONVILLE, Fla. -

For some Jacksonville homeowners, it's become a nightmare. A house they thought they owned now has someone else living in it, claiming to be the new owners.

An old law on the books allows the "new owners" to take possession, but with foreclosure now, the old law has turned into a new concern for homeowners, police and the state attorney.

Legally, it's called adverse possession. Those familiar with the situation call it modern-day squatting.

For example, people have moved into a $1 million riverfront home on the Northside and have paid practically nothing.

The Northside home has been going though foreclosure proceedings for more than a year. The owner, Dale Cole, said he had moved out of the home and was working with a mortgage company to sell it, but he learned from a potential buyer that other people had moved in, claiming they owned the property.

"We started seeing people show up and open the front door in the house. Did not know what was going on," said a neighbor who did not want to give his name. "Never went over to talk to anybody, but it's the darndest thing."

Police were called, and they learned the people moving in filed paperwork for adverse possession. It does not cost anything to file, but the "new owners" claim it allows them to move in and take over the property because it was vacant.

Jacksonville police have been involved in the investigation. Every page of a police report provided by the Jacksonville Sheriff's Office has been redacted. Police say it's an active investigation.

So what are the procedures for adverse possessions?

The old law allows someone to take over property that has been abandoned by a homeowner. The person filing the claim must be upfront on what they are doing and notify the owner that they are taking over the land. They must pay the taxes for seven years and live on the property the whole time. The title will then be transferred to them.

"It's a provision that used to be on the law for people to go squat on property and acquire the property after paying taxes for seven years," said property appraiser Jim Overton.

The latest twist is how people are getting in the homes. Police and the state attorney's office would not comment, only to say the Northside case is an active investigation. But they are trying to find out if those involved broke into the property.

There are currently 17 cases like this in Duval County and hundreds more throughout the state and country.

"I heard of one case in South Florida where one individual filed 100 cases," Overton said. "It is not a big thing here yet, and hopefully it won't be. As the market clears out, this problem should go away."

The man who filed the adverse possession on the Northside home has said in phone interviews that he has followed the rules and has every right to take over the house.

The house is currently empty, and the state attorney's office is checking to see who really owns the property and if there was any criminal intent behind the takeover.

Channel 4 has learned that citations have been issued in this case, but it appears this is the tip of the iceberg. In fact, lawmakers are trying to change these laws so something like this can't happen again.

To read the state statutes regarding the adverse possession laws, click here.