As thousands of troops deployed to the southern border await the arrival of a caravan of migrants heading towards the U.S., border patrol agents in Arizona have already been busy, detaining more than 650 illegal immigrants in just two days this week.

Agents in the Yuma Sector said they detained 654 people – most reportedly being family units or unaccompanied minors from Guatemala - on Monday and Tuesday.

Officials said the groups of illegal immigrants are not believed to be associated with the large caravan of mostly Central American migrants that have prompted the military deployment.

U.S. Customs and Border Protection said Wednesday a group of 55 Central Americans waded across the Colorado River near Yuma and surrendered to agents after walking around vehicle barriers in the area.

“Larger numbers [of illegal immigrants] have started to illegally cross shallow portions of the Colorado River near Yuma,” a press release said.

Vinny Dulesky, the special operations supervisor for Yuma Sector public affairs, told Fox News on Thursday that the majority of the groups came in through the east side of the port of entry and had cut through their metal fences to cross in.

He said he did not know the extent of the damage to the fences, but expected fixing them could cost upwards of $1,600 for each one.

“It can get pricey,” Dulesky said.

CBP said apprehensions in the Yuma Sector are up more than 150 percent compared to the last fiscal year at this time. More than 3,600 people were apprehended in the month of October.

ABOUT A DOZEN MEMBERS OF MIGRANT CARAVAN ARRESTED FOR TRYING TO ILLEGALLY CROSS US BORDER, SOURCE SAYS

Dulseky said they are predominantly seeing family units and unaccompanied minors attempting to enter the U.S. and that the tactics of the illegal immigrants are changing.

“Instead of trying to avoid us, they are running to us, and claim asylum,” he said. “By doing that, it keeps them in the country longer.”

Jessica Vaughan, director of policy studies for the Center for Immigration Studies, told Fox News on Thursday that the numbers were “very concerning and startling,” but consistent with trends across the border.

“Yuma is seeing a huge spike and it’s a concern because they don’t have the facilities to process the cases,” she said, adding a majority of the people detained are released to local charities or even at bus stations because federal facilities are overwhelmed. “Most people apprehended and released are not staying in the area … they go join the illegal immigrant population.”

According to CBP statistics, 60,745 people were apprehended or were deemed inadmissible while attempting to enter the U.S. illegally via the southern border in October, the first month of the fiscal year 2019 – compared to the 34,871 in the same month in fiscal year 2018.

A total of 521,090 people were apprehended at the southern border in fiscal year 2018 – up 125 percent from 451,514 in fiscal year 2017. Just in Yuma, more than 26,000 people were apprehended in fiscal year 2018.

Vaughan said the U.S. immigration system is not equipped to handle such an influx of people all at the same time, and drug cartels and smugglers have taken notice.

“They have identified a route that gets people in and they funnel through as many people,” she said. “They move as much product as possible.”