​Just how bad is the illegal immigration situation in America? In short, worse than you think. An update on the immigration numbers provided recently by Alabama Senator Jeff Sessions shows some deeply troubling developments. FY 2016 saw an over 20 percent increase over the last year in illegal crossings — with 400,000 apprehensions and another estimated 400,000 who slipped through the cracks — a nearly 50 percent spike in unaccompanied juveniles, and a surge in the number of immigrants not from Mexico. Due to the massive influx of illegals, Immigration and Customs Enforcement (ICE) has almost maxed out its detention centers and is threatening to release many of the detainees as a result. Meanwhile, the administration refuses to release many of the details of how it is handling the surge in immigrants, particularly whether or not they are being allowed to stay in the country.

Here are five facts on the illegal immigration crisis from Sessions' report:

1. Over 400,000 illegals were apprehended at the border in FY 2016 — an over 20 percent increase over the last year.

The Border Patrol reported apprehending a total of 408,870 illegals at the southern border in FY 2016, which is a 23 percent increase from the previous year. Among those were 59,692 unaccompanied minors, a 49 percent increase from 2015. Another nearly 77,674 were "family units," which is a 95 percent increase over the previous year. The total number of apprehensions over the last three years equals more than 1.2 million (331,333 in FY 2015 and 479,371 in FY 2014).

2. An estimated 400,000 illegal immigrants slipped through the cracks in 2016.

Citing internal DHS statistics and the testimony of Brandon Judd, President of the American Federation of Government Employees, before the Senate Subcommittee on Immigration and The National Interest this year, Sessions notes that the internal numbers show that "for every one illegal alien who is apprehended, another evades arrest." That puts the estimate at over 400,000 illegals in FY 2016 who were able to enter the country without being detained — and about 1.2 million over the least three years.

3. ICE has almost maxed out its capacity to detain immigrants.

The detention numbers from ICE are increasingly problematic. They're currently holding over 40,000 illegals, with Sessions noting that their internal predictions are pointing to 47,000 "in the coming months." That spells trouble for the already cash-strapped bureau, as the Senator highlights:

An ICE officer in El Paso said "The administration’s policies have created the influx and the crisis situation because people overrun our border knowing they have a chance to stay," the officer said. "The workload, the number of people, we’ve had to deal with has by far surpassed any amount we’ve ever had to handle before."

What will happen to those illegals released? Simply put, the federal government doesn't know, or at least won't admit that it knows, as the statistics show that a majority of them disappear into the "shadows."

4. More immigrants are coming from places other than Mexico, and getting even more impossible to vet.

Agents estimate that 70-75 percent of those entering the country illegally are from places other than Mexico, often making vetting even more difficult. The trend is so strong that "Other Than Mexican" (OTM) has become a common designation used by immigration agents. A lot of the recent OTMs appear to be coming for Haiti and Africa. Here's Sessions' breakdown:

Included among those OTMs are thousands of Haitians and Africans concentrated in the Mexican cities of Tijuana and Mexicali, who are pushing to enter the United States, despite having no valid visa; and roughly 35,000 Cubans who crossed into Texas between October of 2015 and July of this year.

5. The Obama administration refuses to release important information on illegal immigration.

The Obama administration is effectively stonewalling Congress and the American people on crucial immigration numbers, including estimates of those slipping through the cracks and the status and whereabouts of the over one million immigrants detained over the last three years:

The Obama Administration refuses to tell the American people how many of the 408,870 aliens it apprehended in FY 2016 remain in the United States. Nor will it provide information on the current location of the 331,333 it apprehended in FY 2015, or the 479,371 it apprehended in FY 2014. One ICE officer recently explained that ICE is releasing many aliens “into the wind never to be seen by us again[.]”?

As Sessions underscores, despite its deliberate negligence regarding immigration, the Obama Administration continues to insist hat the southern border is "more secure than it has ever been."

Read Sessions' full report here.