The Navy is investigating allegations of a drug ring at the U.S. Naval Academy in Annapolis, Md., involving roughly 10 midshipmen, according to a senior Naval Academy official with knowledge of the investigation.

Three midshipmen are accused of selling cocaine, ketamine (a powerful sedative) and LSD to their classmates purchased on the dark web using Bitcoin, according to three midshipmen currently enrolled at the school.

No formal charges have been brought against the midshipmen during the investigation, which began nearly three months ago after a midshipman reported the drug dealing to authorities.

Midshipmen sources estimated the number of students under investigation to be as high as roughly two-dozen, despite the lower official estimate.

In a sign of how seriously Naval Academy officials are taking the alleged drug use, the second in command of the school, Capt. Robert B. Chadwick II, ordered a surprise drug test for all the midshipmen at 5:30 a.m. Wednesday morning. The entire Brigade of Midshipmen totals 4,500.

Normally, senior midshipmen leaders are given a heads up about drug tests the night before, and the tests are given only at the company level -- involving about 150 midshipmen at a time. Not so in this case, according to one of the midshipmen. Instead, all 4,500 were tested at the same time.

The drug investigation is centered on the 23rd company and its roughly 150 midshipmen, according to several students who agreed to speak to Fox News only on the condition of anonymity because they were not authorized to speak with the media.

Last week, drug-sniffing dogs from the DEA were brought in to search the rooms of the suspected drug users and discovered cocaine. The midshipman suspected of possessing the drug was at athletic practice at the time and she tried to escape but was apprehended and brought in for questioning, according to two midshipmen with knowledge of the incident.

Since charges have not been brought against any of the suspected midshipmen, Fox News is withholding the names of those implicated. Two are prior enlisted midshipmen who had spent time in the fleet before gaining appointment to the Naval Academy, which educates and trains young men and women to become officers in the Navy or Marine Corps. One of the midshipmen tested positive on a drug test in early January after returning from Christmas break, adding more urgency to the investigation, according to one midshipman.

Chadwick recently addressed the brigade at lunch, telling them that while the investigation is ongoing, there would be no more discussion about it, according to several midshipmen present that day.

“The Naval Academy and the Naval Criminal Investigative Service recently initiated a command-assisted investigation in Annapolis after receiving a midshipman report of alleged recreational drug use within the Brigade,” said Cmdr. David Mckinney, a Naval Academy spokesman, in a statement to Fox News. “[T]he results of the investigation are still pending. We are continuing to work with NCIS on these reported allegations. The Navy has a zero tolerance for drug abuse and takes all allegations of misconduct very seriously.”

The Navy investigation into alleged drug use at the Naval Academy was first mentioned in a report by Fox 45 in Baltimore on Tuesday.

The Annapolis Capital also reported that between 2010 and 2011, “NCIS conducted an 11-month investigation into the use of synthetic marijuana, or spice, by midshipmen. That investigation ended the careers of at least 27 midshipmen.”

Naval Academy officials said seven midshipmen were kicked out for drugs between 2010 and 2017.