How does an inmate have a smartphone in the D.C. jail, where he appears to be tweeting and Facebooking to his heart’s content?

That’s a good question, and one that several readers and Tweeters have asked me since my story about an accused drug kingpin at the D.C. jail ran online and in Saturday’s paper.

The Post sought to interview Thomas Faust, director of the D.C. Department of Corrections, but that request was declined by his spokeswoman, Sylvia Lane.

Lane also declined to provide statistics on the number of smartphones seized at the D.C. jail. (We will be filing a public records request today for that information.)

Cell phone use by prisoners has grown dramatically across the nation in recent years. The problem concerns law enforcement officials because the devices allow inmates to run criminal organizations and intimidate witnesses from behind bars.

The number of phones seized in federal prisons has surged — in 2010, authorities confiscated more than 8,000 such devices from inmates.

In response, states and the federal government have passed laws banning possession of cell phones by inmates and making it a crime to give them one.

Experts say the largest and most reliable source of such devices for inmates are corrupt guards, who can make a pretty profit in the jail “cell” trade. (Inmates have also been known to get such devices from visitors and in the mail.)

“A big part of it is corrections officers,” said William Sondervan, a former top Maryland corrections official who is a professor at the University of Maryland University College. “The inmates pay off corrections officers and sneak them in. Some of these inmates made a lot of money on the outside. Most corrections officers are pretty honest. But a few of them will smuggle them in for money.”

An inspector general’s report in California documented that a guard made $150,000 a year in slipping phones to inmates.

In D.C., officials have also taken steps to combat the problem, Lane said, providing this e-mailed statement (DOC is Department of Corrections and MPD is D.C. police):

• For the first time ever, DOC and MPD teamed up in a major joint operation involving mass shakedowns and cell searches of the facility. Two of these joint operations have been conducted to date.

• There are three K-9 officers assigned to the facility specifically to conduct daily searches. In addition to drug detection, two of the dogs have undergone special training for cell phone detection.

• Since coming on board, Director Faust has created a six-man shakedown team primarily responsible for conducting security searches and shakedowns on a daily basis.

Follow Del on Twitter @delwilber.

Read more: The Post’s crime coverage