His arrest warrant, which was obtained by ESPNDallas.com, states that an undercover police officer bought marijuana from Horn and Yendrey at their residence on Nov. 3, 2011.

The investigation continued for several months, and on Jan. 18, the officer asked to purchase a half-ounce of marijuana from Yendrey. The warrant states that Yendrey said he was out, but a friend could get the drugs. The officer then was able to buy marijuana from a man who turned out to be Brock.

The officer allegedly again bought marijuana from Brock a few days later. On Feb. 1, the officer was alerted by the TCU police force that the football team was surprised with a drug test. The officer contacted Brock and spoke about the test on the phone.

"Ya, they caught us slipping," Brock allegedly said.

The officer went to Brock's residence and bought $220 worth of marijuana, according to the warrant. The officer told Brock that the drug test was "bull----," and Brock responded, "I failed that b---- for sure."

According to the warrant, Brock said that he wasn't worried because there "would be about 60 people being screwed." Brock is alleged to have said that he and Horn had looked over the TCU roster and concluded that only about 20 players could pass the test.

The officer then asked Brock if he could get him any Xanax or hydrocodone pills. According to the warrant, Brock said he knew a girl who could get them and that he used to buy pills from two other football players, but they had graduated.

In response to that allegation, TCU cornerback Kolby Griffin posted a tweet on his personal account Wednesday that read, "This rumor about 82 of us failing a drug test is false completely false."

TCU released a statement late Wednesday afternoon that said the school tests its athletes for drug use "on a regular basis."

"The comments about failed drug tests made by the separated players in affidavits cannot be verified simply because they were made in the context of a drug buy," the school said. Football coach Gary Patterson declined to answer questions beyond a prepared statement.

Patterson ordered the drug test Feb. 1 -- national signing day -- after a recruit said he would not play for TCU because of players' drug use, the Fort Worth Star-Telegram reported Wednesday, citing anonymous sources. TCU police chief Steve McGee said that the investigation was prompted by complaints from players, students and parents.

Johnson started eight games in 2011 and had 47 tackles and 2½ sacks. Yendrey led TCU interior linemen in tackles in 2011 and was honorable mention All-Mountain West. Horn was expected to compete for a starting spot in 2012.

The investigation will continue after the sweeping drug sting, and there could be more arrests, according to TCU chancellor Victor J. Boschini Jr.

Three of the students were arrested on campus; 14 were arrested off-campus. Boschini said the school has never experienced a mass arrest such as this.

"I'm extremely concerned," Boschini said. "If one kid is involved, it's one kid too many."

Patterson and athletic director Chris Del Conte both said TCU student-athletes are expected to be ambassadors for the university, and that drug use and criminal behavior would not be tolerated.

"There are days people want to be a head football coach, but today is not one of those days," Patterson said in a prepared statement. "As I heard the news this morning, I was first shocked, then hurt and now I'm mad.

"Under my watch, drugs and drug use by TCU's student-athletes will not be tolerated by me or any member of my coaching staff. Period. Our program is respected nationally for its strong ethics and for that reason the players arrested today were separated from TCU by the University.

"I believe strongly that young people's lives are more important than wins or losses."

Patterson said the team has programs in place to help players make smart choices.

"At the end of the day, though, sometimes young people make poor choices. The Horned Frogs are bigger and stronger than those involved," he said.

Said Del Conte: "Our student-athletes are a microcosm of society and unfortunately that means some of our players reflect a culture that glorifies drugs and drug use. That mindset is not reflected by TCU nor will it be allowed within athletics."

The investigation began about six months ago, and the Fort Worth police worked with the TCU campus police. McGee said the students arrested Wednesday were caught in an undercover operation selling marijuana, cocaine, Ecstasy and prescription drugs.

Officials say all 17 students have been taken off the school's Fort Worth campus.

"This is a very clear message to everybody that if you want to do this kind of thing, you can't go to TCU," Boschini said.

The Horned Frogs are set to join the Big 12 later this year in a move expected to be a boon for their athletic program. Boschini was asked if he's concerned about the football team being scrutinized.

"I'm concerned about the safety and health of our campus and if anyone is involved in this, they have to undergo that scrutiny," Boschini said. "I don't think it's a football problem. It's four people on the football team."

He called the entire episode "very disheartening."

"We expect more of our students, faculty and staff and that's the message we've given them today," Boschini said. "And 99.9 percent of the students here do the right thing and we want to make sure the ones that don't aren't at TCU."

TCU, also known as Texas Christian University, is a private institution affiliated with The Christian Church (Disciples of Christ), a Protestant denomination. On its website, the university said 71 students -- less than 1 percent of the student body of approximately 9,500 -- were disciplined for drug law violations in 2011.

Richard Durrett is a reporter for ESPNDallas.com. Information from ESPNDallas.com's Jeff Caplan and The Associated Press was used in this report.