SAN DIEGO - Undercover agents who posed as college students to bust more than 100 suspected drug dealers at San Diego State University never had to crack a book to gain acceptance on campus. All it took was cash.

The federal agents went to one or two parties but never went to class or lived in the dorms. Instead, they merely arranged meetings with suspected dealers and asked about buying cocaine, ecstasy, methamphetamine, marijuana and other drugs, authorities said Wednesday.

"All it took was saying, 'Hey, I go to State, can you hook me up?' " said San Diego County prosecutor Damon Mosler. "And then it was off to the races."

The day after the drug sweep landed members of three fraternities in jail and led to the suspension of six frats, investigators revealed how easy it was to penetrate the university's drug culture.

Students who had gotten caught for fighting, drinking, minor drug offenses or other crimes quickly turned informants and used text messages to introduce their drug dealers to undercover agents. Dealers made handoffs in front of dorms, in parking lots or behind frat houses, sometimes in broad daylight in full view of surveillance cameras.

They apparently made little effort to launder their spoils. One fraternity brother arrested Tuesday drove his Lexus directly from a $400 cocaine sale on campus to a nearby bank, where he deposited the cash, according to court papers.

That came as a surprise to agents from the Drug Enforcement Administration, who were used to being thoroughly screened by dealers scared of being arrested.

"They never gave any thought that we could be doing an operation there," said Eileen Zeidler, a spokeswoman for the DEA office in San Diego.

At least 75 people arrested during the five-month sting were San Diego State students, and 13 of them were from seven fraternities. All together, there were 128 arrests, 61 on Tuesday. Theta Chi had the highest number of students arrested, with five.

Campus police started the probe a year ago after the cocaine overdose death of a freshman sorority member, but they soon called in federal agents to provide fresh faces on campus and supply the money needed to make drug buys.

That was a major departure from the arms'-length relationship that has existed between colleges and police since the 1960s. For decades, police in many communities have largely turned a blind eye to drugs on campus.